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@@ -29,6 +29,7 @@ Some aspects of the library can be configured by defining preprocessor macros **
- [**JSON_NO_IO**](https://json.nlohmann.me/api/macros/json_no_io/index.md) - switch off functions relying on certain C++ I/O headers
- [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](https://json.nlohmann.me/api/macros/json_skip_unsupported_compiler_check/index.md) - do not warn about unsupported compilers
- [**JSON_USE_GLOBAL_UDLS**](https://json.nlohmann.me/api/macros/json_use_global_udls/index.md) - place user-defined string literals (UDLs) into the global namespace
- [**JSON_USE_SIMDUTF**](https://json.nlohmann.me/api/macros/json_use_simdutf/index.md) - use the simdutf library to accelerate UTF-8 validation
## Library version
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_assert/" rel="canonical"><link href=../ rel=prev><link href=../json_brace_init_copy_semantics/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_ASSERT - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> JSON_ASSERT </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio 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6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></Line truncated
</code></pre></div> <p>This macro controls which code is executed for <a href=../../../features/assertions/ >runtime assertions</a> of the library.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>x</code> (in)</dt> <dd>expression of a scalar type</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <a href="https://en.cppreference.com/w/cpp/error/assert"><code class=highlight><span class=n>assert</span><span class=p>(</span><span class=n>x</span><span class=p>)</span></code></a>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_ASSERT(x) assert(x)</span>
</code></pre></div> <p>Therefore, assertions can be switched off by defining <code>NDEBUG</code>.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <ul> <li>The library uses numerous assertions to guarantee invariants and to abort in case of otherwise undefined behavior (e.g., when calling <a href=../../basic_json/operator%5B%5D/ >operator[]</a> with a missing object key on a <code>const</code> object). See page <a href=../../../features/assertions/ >runtime assertions</a> for more information.</li> <li>Defining the macro to code that does not call <code>std::abort</code> may leave the library in an undefined state.</li> <li>The macro is undefined outside the library.</li> </ul> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example 1: default behavior</summary> <p>The following code will trigger an assertion at runtime:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -24,4 +24,4 @@
<span class=w> </span><span class=k>auto</span><span class=w> </span><span class=n>v</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>"missing"</span><span class=p>];</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code>assertion error in operator[]
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/assertions/ >Runtime Assertions</a> - overview documentation</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.9.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/assertions/ >Runtime Assertions</a> - overview documentation</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.9.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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@@ -1,4 +1,4 @@
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</code></pre></div> <p>When defined to <code>1</code>, single-element brace initialization of a <code>basic_json</code> value is treated as a copy/move of the element rather than wrapping it in a single-element array.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (disabled — existing behavior is preserved).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_BRACE_INIT_COPY_SEMANTICS 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Background</p> <p>C++ always prefers the <code>initializer_list</code> constructor over the copy/move constructor for brace initialization. This means that code like</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>obj</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=p>{{</span><span class=s>"key"</span><span class=p>,</span><span class=w> </span><span class=s>"value"</span><span class=p>}};</span>
<span class=n>json</span><span class=w> </span><span class=n>j</span><span class=p>{</span><span class=n>obj</span><span class=p>};</span>
@@ -26,4 +26,4 @@
<span class=w> </span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=p>{</span><span class=n>obj</span><span class=p>};</span>
<span class=w> </span><span class=c1>// j is {"key":"value"} -- copy of obj</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/faq/#brace-initialization-yields-arrays><abbr title="Frequently Asked Questions">FAQ</abbr>: Brace initialization yields arrays</a></li> <li><a href=../../basic_json/basic_json/ ><strong>basic_json(initializer_list_t)</strong></a> - the affected constructor</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/faq/#brace-initialization-yields-arrays><abbr title="Frequently Asked Questions">FAQ</abbr>: Brace initialization yields arrays</a></li> <li><a href=../../basic_json/basic_json/ ><strong>basic_json(initializer_list_t)</strong></a> - the affected constructor</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>This macro enables position diagnostics for generated <abbr title="JavaScript Object Notation">JSON</abbr> objects.</p> <p>When enabled, two new member functions <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> and <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> are added to <a href=../../basic_json/ ><code>basic_json</code></a> values. If the value was created by calling the<a href=../../basic_json/parse/ ><code>parse</code></a> function, then these functions allow querying the byte positions of the value in the input it was parsed from. In case the value was constructed by other means, <code>std::string::npos</code> is returned.</p> <p><a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> returns the position of the first character of a given value in the original <abbr title="JavaScript Object Notation">JSON</abbr> string, while <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> returns the position of the character <em>following</em> the last character. For objects and arrays, the first and last characters correspond to the opening or closing braces/brackets, respectively. For primitive values, the first and last character represents the opening and closing quotes (strings) or the first and last character of the field's numerical or predefined value (<code>true</code>, <code>false</code>, <code>null</code>), respectively.</p> <table> <thead> <tr> <th><abbr title="JavaScript Object Notation">JSON</abbr> type</th> <th>return value <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a></th> <th>return value <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a></th> </tr> </thead> <tbody> <tr> <td>object</td> <td>position of the opening <code>{</code></td> <td>position after the closing <code>}</code></td> </tr> <tr> <td>array</td> <td>position of the opening <code>[</code></td> <td>position after the closing <code>]</code></td> </tr> <tr> <td>string</td> <td>position of the opening <code>"</code></td> <td>position after the closing <code>"</code></td> </tr> <tr> <td>number</td> <td>position of the first character</td> <td>position after the last character</td> </tr> <tr> <td>boolean</td> <td>position of <code>t</code> for <code>true</code> and <code>f</code> for <code>false</code></td> <td>position after <code>e</code></td> </tr> <tr> <td>null</td> <td>position of <code>n</code></td> <td>position after <code>l</code></td> </tr> </tbody> </table> <p>Given the above, <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a><code>-</code><a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> for a <abbr title="JavaScript Object Notation">JSON</abbr> value provides the length of the parsed <abbr title="JavaScript Object Notation">JSON</abbr> string for that value, including the opening or closing braces, brackets, or quotes.</p> <p>Note that enabling this macro increases the size of every <abbr title="JavaScript Object Notation">JSON</abbr> value by two <code>std::size_t</code> fields and adds slight runtime overhead to parsing, copying <abbr title="JavaScript Object Notation">JSON</abbr> value objects, and the generation of error messages for exceptions. It also causes these values to be reported in those error messages.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (position diagnostics are switched off).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DIAGNOSTIC_POSITIONS 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>CMake option</p> <p>Diagnostic positions can also be controlled with the CMake option <a href=../../../integration/cmake/#json_diagnostic_positions><code>JSON_Diagnostic_Positions</code></a> (<code>OFF</code> by default) which defines <code>JSON_DIAGNOSTIC_POSITIONS</code> accordingly.</p> </div> <div class="admonition note"> <p class=admonition-title>Availability</p> <p>Diagnostic positions are only available if the value was created by the <a href=../../basic_json/parse/ ><code>parse</code></a> function. The <a href=../../basic_json/sax_parse/ ><code>sax_parse</code></a> function or all other means to create a <abbr title="JavaScript Object Notation">JSON</abbr> value <strong>do not</strong> set the diagnostic positions and <a href=../../basic_json/start_pos/ ><code>start_pos()</code></a> and <a href=../../basic_json/end_pos/ ><code>end_pos()</code></a> will only return <code>std::string::npos</code> for these values.</p> </div> <div class="admonition warning"> <p class=admonition-title>Invalidation</p> <p>The returned positions are only valid as long as the <abbr title="JavaScript Object Notation">JSON</abbr> value is not changed. The positions are <em>not</em> updated when the <abbr title="JavaScript Object Notation">JSON</abbr> value is changed.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: retrieving positions</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
@@ -165,4 +165,4 @@ Parsed string:
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code>[json.exception.type_error.302] (/address/housenumber) (bytes 92-95) type must be number, but is string
</code></pre></div> <div class=codehilite><pre><span></span><code>The output shows the exception with diagnostic path info and start/end positions.
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_diagnostic_positions><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_Diagnostic_Positions</a> - CMake option to control the macro</li> <li><a href=../json_diagnostics/ >JSON_DIAGNOSTICS</a> - macro to control extended diagnostics</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.12.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_diagnostic_positions><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_Diagnostic_Positions</a> - CMake option to control the macro</li> <li><a href=../json_diagnostics/ >JSON_DIAGNOSTICS</a> - macro to control extended diagnostics</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.12.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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+2 -2
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@@ -1,4 +1,4 @@
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</code></pre></div> <p>This macro enables <a href=../../../home/exceptions/#extended-diagnostic-messages>extended diagnostics for exception messages</a>. Possible values are <code>1</code> to enable or <code>0</code> to disable (default).</p> <p>When enabled, exception messages contain a <a href=../../json_pointer/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> to the <abbr title="JavaScript Object Notation">JSON</abbr> value that triggered the exception. Note that enabling this macro increases the size of every <abbr title="JavaScript Object Notation">JSON</abbr> value by one pointer and adds some runtime overhead.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code> (extended diagnostics are switched off).</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DIAGNOSTICS 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>As of version 3.11.0, this macro is no longer required to be defined consistently throughout a codebase to avoid One Definition Rule (ODR) violations, as the value of this macro is encoded in the namespace, resulting in distinct symbol names. </p> <p>This allows different parts of a codebase to use different versions or configurations of this library without causing improper behavior.</p> <p>Where possible, it is still recommended that all code define this the same way for maximum interoperability.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Diagnostic messages can also be controlled with the CMake option <a href=../../../integration/cmake/#json_diagnostics><code>JSON_Diagnostics</code></a> (<code>OFF</code> by default) which defines <code>JSON_DIAGNOSTICS</code> accordingly. Note this only applies when building the library from source — see the pre-installed-package caveat on that page.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example 1: default behavior</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -75,4 +75,4 @@
<span class=w> </span><span class=p>}</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <p><div class=highlight><pre><span></span><code>[json.exception.type_error.302] (bytes 92-95) type must be number, but is string
</code></pre></div> The output shows the exception with start/end positions only.</p> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_diagnostics><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_Diagnostics</a> - CMake option to control the macro</li> <li><a href=../json_diagnostic_positions/ >JSON_DIAGNOSTIC_POSITIONS</a> - macro to access positions of elements</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.10.0.</li> <li>As of version 3.11.0, the definition is allowed to vary between translation units.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> The output shows the exception with start/end positions only.</p> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_diagnostics><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_Diagnostics</a> - CMake option to control the macro</li> <li><a href=../json_diagnostic_positions/ >JSON_DIAGNOSTIC_POSITIONS</a> - macro to access positions of elements</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.10.0.</li> <li>As of version 3.11.0, the definition is allowed to vary between translation units.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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@@ -1,4 +1,4 @@
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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> JSON_DISABLE_ENUM_SERIALIZATION </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo 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</code></pre></div> <p>When defined to <code>1</code>, default serialization and deserialization functions for enums are excluded and have to be provided by the user, for example, using <a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a> (see <a href=../../../features/arbitrary_types/ >arbitrary type conversions</a> for more details).</p> <p>Parsing or serializing an enum will result in a compiler error.</p> <p>This works for both unscoped and scoped enums.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_ENUM_SERIALIZATION 0</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Enum serialization can also be controlled with the CMake option <a href=../../../integration/cmake/#json_disableenumserialization><code>JSON_DisableEnumSerialization</code></a> (<code>OFF</code> by default) which defines <code>JSON_DISABLE_ENUM_SERIALIZATION</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example 1: Disabled behavior</summary> <p>The code below forces the library <strong>not</strong> to create default serialization/deserialization functions <code>from_json</code> and <code>to_json</code>, meaning the code below <strong>does not</strong> compile.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_ENUM_SERIALIZATION 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -88,4 +88,4 @@
<span class=w> </span><span class=c1>// uses user-defined from_json function</span>
<span class=w> </span><span class=n>Choice</span><span class=w> </span><span class=n>ch</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>get</span><span class=o>&lt;</span><span class=n>Choice</span><span class=o>&gt;</span><span class=p>();</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_disableenumserialization><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_DisableEnumSerialization</a> - CMake option to control the macro</li> <li><a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a> - serialize/deserialize an enum</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_disableenumserialization><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_DisableEnumSerialization</a> - CMake option to control the macro</li> <li><a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a> - serialize/deserialize an enum</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<span class=cp>#define JSON_HAS_CPP_14</span>
<span class=cp>#define JSON_HAS_CPP_17</span>
<span class=cp>#define JSON_HAS_CPP_20</span>
@@ -8,4 +8,4 @@
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.10.5.</li> <li>Added <code>JSON_HAS_CPP_23</code> in version 3.12.0.</li> <li>Added <code>JSON_HAS_CPP_26</code> in version 3.13.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.10.5.</li> <li>Added <code>JSON_HAS_CPP_23</code> in version 3.12.0.</li> <li>Added <code>JSON_HAS_CPP_26</code> in version 3.13.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<span class=cp>#define JSON_HAS_EXPERIMENTAL_FILESYSTEM </span><span class=cm>/* value */</span>
</code></pre></div> <p>When compiling with C++17, the library provides conversions from and to <a href="https://en.cppreference.com/w/cpp/filesystem/path"><code>std::filesystem::path</code></a>. As compiler support for filesystem is limited, the library tries to detect whether <a href="https://en.cppreference.com/w/cpp/header/filesystem"><code>&lt;filesystem&gt;</code>/<code>std::filesystem</code></a> (<code>JSON_HAS_FILESYSTEM</code>) or <a href="https://en.cppreference.com/w/cpp/header/experimental/filesystem"><code>&lt;experimental/filesystem&gt;</code>/<code>std::experimental::filesystem</code></a> (<code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code>) should be used. To override the built-in check, define <code>JSON_HAS_FILESYSTEM</code> or <code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code> to <code>1</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>__cpp_lib_filesystem</span></code>, <code class=highlight><span class=n>__cpp_lib_experimental_filesystem</span></code>, <code class=highlight><span class=n>__has_include</span><span class=p>(</span><span class=o>&lt;</span><span class=n>filesystem</span><span class=o>&gt;</span><span class=p>)</span></code>, or <code class=highlight><span class=n>__has_include</span><span class=p>(</span><span class=o>&lt;</span><span class=n>experimental</span><span class=o>/</span><span class=n>filesystem</span><span class=o>&gt;</span><span class=p>)</span></code>.</p> <div class="admonition info"> <p class=admonition-title>Known compiler/stdlib exclusions</p> <p>Even when the feature-test macro indicates filesystem support is available, the library disables it on the following broken toolchains:</p> <ul> <li><strong>MinGW + <abbr title="GNU Compiler Collection">GCC</abbr> 8</strong> — disabled entirely (broken <code>std::filesystem</code> implementation; <a href="https://sourceforge.net/p/mingw-w64/bugs/737/">MinGW-w64 bug 737</a>)</li> <li><strong><abbr title="GNU Compiler Collection">GCC</abbr> (non-Clang) &lt; 8</strong> — disabled (no filesystem support)</li> <li><strong>Clang &lt; 7</strong> — disabled (no filesystem support)</li> <li><strong><abbr title="Microsoft Visual C++">MSVC</abbr> &lt; 19.14</strong> — disabled (no filesystem support)</li> <li><strong>iOS &lt; 13</strong> — disabled (no filesystem support)</li> <li><strong>macOS &lt; Catalina (10.15)</strong> — disabled (no filesystem support)</li> </ul> <p>If <code>JSON_HAS_FILESYSTEM</code> or <code>JSON_HAS_EXPERIMENTAL_FILESYSTEM</code> is <code>0</code> despite <code>__cpp_lib_filesystem</code> being defined, one of the exclusions above likely applies to your toolchain.</p> </div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <ul> <li>Note that older compilers or older versions of libstdc++ also require the library <code>stdc++fs</code> to be linked to for filesystem support.</li> <li>Both macros are undefined outside the library.</li> </ul> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to use the header <code>&lt;experimental/filesystem&gt;</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
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</code></pre></div> <p>This macro indicates whether the standard library has any support for ranges. Implies support for concepts. Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macro <code class=highlight><span class=n>__cpp_lib_ranges</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <div class="admonition info"> <p class=admonition-title>Known compiler/stdlib exclusions</p> <p>Even when the feature-test macro <code>__cpp_lib_ranges</code> indicates ranges support is available, the library disables it on the following incomplete or broken toolchains:</p> <ul> <li><strong><abbr title="GNU Compiler Collection">GCC</abbr> 11.1.0</strong> — disabled (the shipped <code>&lt;ranges&gt;</code> header has a syntax error; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>libstdc++ &lt; 11</strong> — disabled (incomplete C++20 ranges support; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>Clang &lt; 16 with libstdc++</strong> — disabled (incomplete ranges support; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>libc++ &lt; 160000</strong> — disabled (incomplete C++20 ranges support; <a href="https://github.com/nlohmann/json/issues/4440">issue #4440</a>)</li> <li><strong>nvcc (CUDA) 12.0.x and 12.1.x</strong> — disabled (the <code>enable_borrowed_range</code> variable-template syntax triggers a parse error under these two toolkit versions; fixed in CUDA 12.2; <a href="https://github.com/nlohmann/json/issues/3907">issue #3907</a>)</li> </ul> <p>If <code>JSON_HAS_RANGES</code> is <code>0</code> despite <code>__cpp_lib_ranges</code> being defined, one of the exclusions above likely applies to your toolchain.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to enable support for ranges:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_RANGES 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
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</code></pre></div> <p>This macro indicates whether the standard library has any support for <abbr title="Runtime Type Information">RTTI</abbr> (run time type information). Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macro <code class=highlight><span class=n>_HAS_STATIC_RTTI</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to enable support for libraries with <abbr title="Runtime Type Information">RTTI</abbr> dependence:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_STATIC_RTTI 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.3.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_has_std_format/" rel="canonical"><link href=../json_has_static_rtti/ rel=prev><link href=../json_has_three_way_comparison/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_HAS_STD_FORMAT - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>This macro indicates whether the standard library has support for <code>std::format</code>/<code>std::formatter</code> (that is, the <code>&lt;format&gt;</code> header). Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>JSON_HAS_CPP_20</span></code> and <code class=highlight><span class=n>__cpp_lib_format</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Enabled functionality</p> <p>When this macro evaluates to <code>1</code>, the library provides a <a href=../../basic_json/std_formatter/ ><code>std::formatter&lt;basic_json&gt;</code></a> specialization so <abbr title="JavaScript Object Notation">JSON</abbr> values can be used directly with <code>std::format</code>.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to disable support for <code>std::format</code>, even if the standard library would otherwise support it:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_STD_FORMAT 0</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
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</code></pre></div> <p>This macro indicates whether the compiler and standard library support 3-way comparison. Possible values are <code>1</code> when supported or <code>0</code> when unsupported.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is detected based on the preprocessor macros <code class=highlight><span class=n>__cpp_impl_three_way_comparison</span></code> and <code class=highlight><span class=n>__cpp_lib_three_way_comparison</span></code>.</p> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library to use 3-way comparison:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_HAS_THREE_WAY_COMPARISON 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
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</code></pre></div> <p>When defined, headers <code>&lt;cstdio&gt;</code>, <code>&lt;ios&gt;</code>, <code>&lt;iosfwd&gt;</code>, <code>&lt;istream&gt;</code>, and <code>&lt;ostream&gt;</code> are not included and parse functions relying on these headers are excluded. This is relevant for environments where these I/O functions are disallowed for security reasons (e.g., Intel Software Guard Extensions (SGX)).</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_NO_IO</span></code> is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NO_IO</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below forces the library not to use the headers <code>&lt;cstdio&gt;</code>, <code>&lt;ios&gt;</code>, <code>&lt;iosfwd&gt;</code>, <code>&lt;istream&gt;</code>, and <code>&lt;ostream&gt;</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NO_IO 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.10.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>Exceptions can be switched off by defining the symbol <code>JSON_NOEXCEPTION</code>. When defining <code>JSON_NOEXCEPTION</code>, <code class=highlight><span class=k>try</span></code> is replaced by <code class=highlight><span class=k>if</span><span class=w> </span><span class=p>(</span><span class=nb>true</span><span class=p>)</span></code>, <code class=highlight><span class=k>catch</span></code> is replaced by <code class=highlight><span class=k>if</span><span class=w> </span><span class=p>(</span><span class=nb>false</span><span class=p>)</span></code>, and <code class=highlight><span class=k>throw</span></code> is replaced by <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>abort</span><span class=p>()</span></code>.</p> <p>The same effect is achieved by setting the compiler flag <code>-fno-exceptions</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NOEXCEPTION</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <p>The explanatory <a href="https://en.cppreference.com/w/cpp/error/exception/what"><code>what()</code></a> string of exceptions is not available for <abbr title="Microsoft Visual C++">MSVC</abbr> if exceptions are disabled, see <a href="https://github.com/nlohmann/json/discussions/2824">#2824</a>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches off exceptions in the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NOEXCEPTION 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/exceptions/#switch-off-exceptions>Switch off exceptions</a> for more information how to switch off exceptions</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 2.1.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/exceptions/#switch-off-exceptions>Switch off exceptions</a> for more information how to switch off exceptions</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 2.1.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>When defined, the library will not create a compiler warning when a different version of the library was already included.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_SKIP_LIBRARY_VERSION_CHECK</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition danger"> <p class=admonition-title>ABI compatibility</p> <p>Mixing different library versions in the same code can be a problem as the different versions may not be ABI compatible.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches off the warning about including a different version of the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_SKIP_LIBRARY_VERSION_CHECK 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <div class="admonition example"> <p class=admonition-title>Example</p> <p>The following warning will be shown in case a different version of the library was already included:</p> <div class=highlight><pre><span></span><code>Already included a different version of the library!
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</code></pre></div> <p>When defined, the library will not create a compile error when a known unsupported compiler is detected. This allows using the library with compilers that do not fully support C++11 and may only work if unsupported features are not used.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, the macro is not defined.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_SKIP_UNSUPPORTED_COMPILER_CHECK</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches off the check whether the compiler is supported.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_SKIP_UNSUPPORTED_COMPILER_CHECK 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 3.2.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_throw_user/" rel="canonical"><link href=../json_brace_init_copy_semantics/ rel=prev><link href=../json_diagnostics/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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<span class=cp>#define JSON_CATCH_USER(exception) </span><span class=cm>/* value */</span>
<span class=c1>// (2)</span>
<span class=cp>#define JSON_THROW_USER(exception) </span><span class=cm>/* value */</span>
@@ -21,4 +21,4 @@
<span class=cp> std::abort();}</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/exceptions/#switch-off-exceptions>Switch off exceptions</a> for more information how to switch off exceptions</li> <li><a href=../json_noexception/ >JSON_NOEXCEPTION</a> - switch off exceptions</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.1.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../home/exceptions/#switch-off-exceptions>Switch off exceptions</a> for more information how to switch off exceptions</li> <li><a href=../json_noexception/ >JSON_NOEXCEPTION</a> - switch off exceptions</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.1.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>When defined to <code>1</code>, the user-defined string literals (UDLs) are placed into the global namespace instead of <code>nlohmann::literals::json_literals</code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>1</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_GLOBAL_UDLS 1</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Future behavior change</p> <p>The user-defined string literals will be removed from the global namespace in the next major release of the library.</p> <p>To prepare existing code, define <code>JSON_USE_GLOBAL_UDLS</code> to <code>0</code> and bring the string literals into scope where needed. Refer to any of the <a href=#see-also>string literals</a> for details.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>The placement of user-defined string literals can also be controlled with the CMake option <a href=../../../integration/cmake/#json_globaludls><code>JSON_GlobalUDLs</code></a> (<code>ON</code> by default) which defines <code>JSON_USE_GLOBAL_UDLS</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example 1: Default behavior</summary> <p>The code below shows the default behavior using the <code>_json</code> UDL.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -29,4 +29,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=mi>42</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../operator_literal_json/ ><code>operator""_json</code></a></li> <li><a href=../../operator_literal_json_pointer/ ><code>operator""_json_pointer</code></a></li> <li><a href=../../../integration/cmake/#json_globaludls><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_GlobalUDLs</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../operator_literal_json/ ><code>operator""_json</code></a></li> <li><a href=../../operator_literal_json_pointer/ ><code>operator""_json_pointer</code></a></li> <li><a href=../../../integration/cmake/#json_globaludls><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_GlobalUDLs</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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@@ -1,7 +1,7 @@
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</code></pre></div> <p>When defined to <code>0</code>, implicit conversions are switched off. By default, implicit conversions are switched on. The value directly affects <a href=../../basic_json/operator_ValueType/ ><code>operator ValueType</code></a>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, implicit conversions are enabled.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_IMPLICIT_CONVERSIONS 1</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition info"> <p class=admonition-title>Future behavior change</p> <p>Implicit conversions will be switched off by default in the next major release of the library.</p> <p>You can prepare existing code by already defining <code>JSON_USE_IMPLICIT_CONVERSIONS</code> to <code>0</code> and replace any implicit conversions with calls to <a href=../../basic_json/get/ ><code>get</code></a>.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Implicit conversions can also be controlled with the CMake option <a href=../../../integration/cmake/#json_implicitconversions><code>JSON_ImplicitConversions</code></a> (<code>ON</code> by default) which defines <code>JSON_USE_IMPLICIT_CONVERSIONS</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>This is an example for an implicit conversion:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span>
<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>;</span>
</code></pre></div> <p>When <code>JSON_USE_IMPLICIT_CONVERSIONS</code> is defined to <code>0</code>, the code above does no longer compile. Instead, it must be written like this:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span>
<span class=k>auto</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>get</span><span class=o>&lt;</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=o>&gt;</span><span class=p>();</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../basic_json/operator_ValueType/ ><strong>operator ValueType</strong></a> - get a value (implicit)</li> <li><a href=../../basic_json/get/ ><strong>get</strong></a> - get a value (explicit)</li> <li><a href=../../../integration/cmake/#json_implicitconversions><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_ImplicitConversions</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.9.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../basic_json/operator_ValueType/ ><strong>operator ValueType</strong></a> - get a value (implicit)</li> <li><a href=../../basic_json/get/ ><strong>get</strong></a> - get a value (explicit)</li> <li><a href=../../../integration/cmake/#json_implicitconversions><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_ImplicitConversions</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.9.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>This macro enables the (incorrect) legacy comparison behavior of discarded <abbr title="JavaScript Object Notation">JSON</abbr> values. Possible values are <code>1</code> to enable or <code>0</code> to disable (default).</p> <p>When enabled, comparisons involving at least one discarded <abbr title="JavaScript Object Notation">JSON</abbr> value yield results as follows:</p> <table> <thead> <tr> <th><strong>Operator</strong></th> <th><strong>Result</strong></th> </tr> </thead> <tbody> <tr> <td><code>==</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td><code>!=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&lt;</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td><code>&lt;=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&gt;=</code></td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td><code>&gt;</code></td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> </tbody> </table> <p>Otherwise, comparisons involving at least one discarded <abbr title="JavaScript Object Notation">JSON</abbr> value always yield <code class=highlight><span class=nb>false</span></code>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition warning"> <p class=admonition-title>Inconsistent behavior in C++20 and beyond</p> <p>When targeting C++20 or above, enabling the legacy comparison behavior is <em>strongly</em> discouraged.</p> <ul> <li>The 3-way comparison operator (<code>&lt;=&gt;</code>) will always give the correct result (<code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>partial_ordering</span><span class=o>::</span><span class=n>unordered</span></code>) regardless of the value of <code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code>.</li> <li>Overloads for the equality and relational operators emulate the legacy behavior.</li> </ul> <p>Code outside your control may use either 3-way comparison or the equality and relational operators, resulting in inconsistent and unpredictable behavior.</p> <p>See <a href=../../basic_json/operator_spaceship/ ><code>operator&lt;=&gt;</code></a> for more information on 3-way comparison.</p> </div> <div class="admonition warning"> <p class=admonition-title>Deprecation</p> <p>The legacy comparison behavior is deprecated and may be removed in a future major version release.</p> <p>New code should not depend on it and existing code should try to remove or rewrite expressions relying on it.</p> </div> <div class="admonition hint"> <p class=admonition-title>CMake option</p> <p>Legacy comparison can also be controlled with the CMake option <a href=../../../integration/cmake/#json_legacydiscardedvaluecomparison><code>JSON_LegacyDiscardedValueComparison</code></a> (<code>OFF</code> by default) which defines <code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code> accordingly.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below switches on the legacy discarded value comparison behavior in the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_legacydiscardedvaluecomparison><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_LegacyDiscardedValueComparison</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../integration/cmake/#json_legacydiscardedvaluecomparison><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M11.769.066.067 23.206l12.76-10.843zm11.438 23.868L7.471 17.587 0 23.934zm.793-.198L12.298.463l1.719 19.24zM12.893 12.959l-5.025 4.298 5.62 2.248z"/></svg></span> JSON_LegacyDiscardedValueComparison</a> - CMake option to control the macro</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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# JSON_USE_SIMDUTF
```cpp
#define JSON_USE_SIMDUTF
```
When defined, the parser validates the UTF-8 content of JSON strings that come from a **contiguous byte input**
(`std::string`, `std::vector<char>`/`<std::uint8_t>`, string literals, `const char*` ranges, …) using the
[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator. On text with many
non-ASCII characters (e.g. CJK or emoji) this can validate several times faster.
This is an **opt-in external dependency**. The library itself remains header-only and its behavior is unchanged: the
same input is accepted or rejected either way, and every parse error is reported at the same position with the same
message (simdutf is only used to fast-path *valid* runs; anything it flags falls back to the scalar path so the exact
diagnostic is preserved). Streaming inputs (files, `std::istream`, wide strings, user-defined adapters) always use the
scalar path.
When `JSON_USE_SIMDUTF` is defined you must make the `simdutf.h` header available on the include path and link the
simdutf library. When it is not defined, no simdutf header is included and there is no dependency.
!!! note "Requires C++17"
simdutf requires C++17 and its header rejects older standards with an `#!cpp #error`. The backend is therefore only
compiled in from C++17 on. In C++11 and C++14 the macro has no effect and the scalar validator is used, which
accepts and rejects exactly the same input -- only throughput differs. Setting the macro project-wide is therefore
safe even when some translation units are built with an older standard.
!!! warning "Define consistently"
The macro selects between two definitions of the same inline validation function. It must therefore be defined
identically for **every** translation unit that includes the library; mixing translation units that define it with
ones that do not is an ODR violation. Prefer setting it as a compile definition on the target rather than with
`#!cpp #define` in individual source files.
## Default definition
By default, `#!cpp JSON_USE_SIMDUTF` is not defined and the portable C++11 scalar validator is used.
```cpp
#undef JSON_USE_SIMDUTF
```
## Examples
??? example
The code below enables the simdutf backend for UTF-8 validation.
```cpp
#define JSON_USE_SIMDUTF 1
#include <nlohmann/json.hpp>
...
```
The project must also link against simdutf, e.g. with CMake:
```cmake
target_compile_definitions(your_target PRIVATE JSON_USE_SIMDUTF)
target_link_libraries(your_target PRIVATE simdutf::simdutf)
```
!!! hint "Testing this configuration"
The unit tests can be built against the simdutf backend with the CMake option `JSON_TestSimdutf` (`OFF` by
default), which fetches simdutf and defines `JSON_USE_SIMDUTF` for every test target. The `ci_test_simdutf` target
runs the whole test suite in that configuration.
## Version history
- Added in version 3.13.0.
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</code></pre></div> <p>When defined, the parser validates the <abbr title="Unicode Transformation Format">UTF</abbr>-8 content of <abbr title="JavaScript Object Notation">JSON</abbr> strings that come from a <strong>contiguous byte input</strong> (<code>std::string</code>, <code>std::vector&lt;char&gt;</code>/<code>&lt;std::uint8_t&gt;</code>, string literals, <code>const char*</code> ranges, …) using the <a href="https://github.com/simdutf/simdutf">simdutf</a> library instead of the built-in scalar validator. On text with many non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters (e.g. CJK or emoji) this can validate several times faster.</p> <p>This is an <strong>opt-in external dependency</strong>. The library itself remains header-only and its behavior is unchanged: the same input is accepted or rejected either way, and every parse error is reported at the same position with the same message (simdutf is only used to fast-path <em>valid</em> runs; anything it flags falls back to the scalar path so the exact diagnostic is preserved). Streaming inputs (files, <code>std::istream</code>, wide strings, user-defined adapters) always use the scalar path.</p> <p>When <code>JSON_USE_SIMDUTF</code> is defined you must make the <code>simdutf.h</code> header available on the include path and link the simdutf library. When it is not defined, no simdutf header is included and there is no dependency.</p> <div class="admonition note"> <p class=admonition-title>Requires C++17</p> <p>simdutf requires C++17 and its header rejects older standards with an <code class=highlight><span class=cp>#error</span></code>. The backend is therefore only compiled in from C++17 on. In C++11 and C++14 the macro has no effect and the scalar validator is used, which accepts and rejects exactly the same input -- only throughput differs. Setting the macro project-wide is therefore safe even when some translation units are built with an older standard.</p> </div> <div class="admonition warning"> <p class=admonition-title>Define consistently</p> <p>The macro selects between two definitions of the same inline validation function. It must therefore be defined identically for <strong>every</strong> translation unit that includes the library; mixing translation units that define it with ones that do not is an ODR violation. Prefer setting it as a compile definition on the target rather than with <code class=highlight><span class=cp>#define</span></code> in individual source files.</p> </div> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_USE_SIMDUTF</span></code> is not defined and the portable C++11 scalar validator is used.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_USE_SIMDUTF</span>
</code></pre></div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The code below enables the simdutf backend for <abbr title="Unicode Transformation Format">UTF</abbr>-8 validation.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_SIMDUTF 1</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=p>...</span>
</code></pre></div> <p>The project must also link against simdutf, e.g. with CMake:</p> <div class=highlight><pre><span></span><code><span class=nb>target_compile_definitions</span><span class=p>(</span><span class=s>your_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>JSON_USE_SIMDUTF</span><span class=p>)</span>
<span class=nb>target_link_libraries</span><span class=p>(</span><span class=s>your_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>simdutf::simdutf</span><span class=p>)</span>
</code></pre></div> </details> <div class="admonition hint"> <p class=admonition-title>Testing this configuration</p> <p>The unit tests can be built against the simdutf backend with the CMake option <code>JSON_TestSimdutf</code> (<code>OFF</code> by default), which fetches simdutf and defines <code>JSON_USE_SIMDUTF</code> for every test target. The <code>ci_test_simdutf</code> target runs the whole test suite in that configuration.</p> </div> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social_Line truncated
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# JSON_USE_SIMDUTF
```
#define JSON_USE_SIMDUTF
```
When defined, the parser validates the UTF-8 content of JSON strings that come from a **contiguous byte input** (`std::string`, `std::vector<char>`/`<std::uint8_t>`, string literals, `const char*` ranges, …) using the [simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator. On text with many non-ASCII characters (e.g. CJK or emoji) this can validate several times faster.
This is an **opt-in external dependency**. The library itself remains header-only and its behavior is unchanged: the same input is accepted or rejected either way, and every parse error is reported at the same position with the same message (simdutf is only used to fast-path *valid* runs; anything it flags falls back to the scalar path so the exact diagnostic is preserved). Streaming inputs (files, `std::istream`, wide strings, user-defined adapters) always use the scalar path.
When `JSON_USE_SIMDUTF` is defined you must make the `simdutf.h` header available on the include path and link the simdutf library. When it is not defined, no simdutf header is included and there is no dependency.
Requires C++17
simdutf requires C++17 and its header rejects older standards with an `#error`. The backend is therefore only compiled in from C++17 on. In C++11 and C++14 the macro has no effect and the scalar validator is used, which accepts and rejects exactly the same input -- only throughput differs. Setting the macro project-wide is therefore safe even when some translation units are built with an older standard.
Define consistently
The macro selects between two definitions of the same inline validation function. It must therefore be defined identically for **every** translation unit that includes the library; mixing translation units that define it with ones that do not is an ODR violation. Prefer setting it as a compile definition on the target rather than with `#define` in individual source files.
## Default definition
By default, `JSON_USE_SIMDUTF` is not defined and the portable C++11 scalar validator is used.
```
#undef JSON_USE_SIMDUTF
```
## Examples
Example
The code below enables the simdutf backend for UTF-8 validation.
```
#define JSON_USE_SIMDUTF 1
#include <nlohmann/json.hpp>
...
```
The project must also link against simdutf, e.g. with CMake:
```
target_compile_definitions(your_target PRIVATE JSON_USE_SIMDUTF)
target_link_libraries(your_target PRIVATE simdutf::simdutf)
```
Testing this configuration
The unit tests can be built against the simdutf backend with the CMake option `JSON_TestSimdutf` (`OFF` by default), which fetches simdutf and defines `JSON_USE_SIMDUTF` for every test target. The `ci_test_simdutf` target runs the whole test suite in that configuration.
## Version history
- Added in version 3.13.0.
@@ -1,4 +1,4 @@
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/" rel="canonical"><link href=../json_use_simdutf/ rel=prev><link href=../nlohmann_define_type_intrusive/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link 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NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input 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<span class=cp>#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE(type, base_type, member...)</span>
<span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT(type, base_type, member...)</span>
@@ -86,4 +86,4 @@
<span class=w> </span><span class=nt>"Ba"</span><span class=p>:</span><span class=w> </span><span class=mi>23</span><span class=p>,</span>
<span class=w> </span><span class=nt>"Bb"</span><span class=p>:</span><span class=w> </span><span class=mi>42</span>
<span class=p>}</span>
</code></pre></div> <p>Notes:</p> <ul> <li><code>A</code> and <code>B</code> are default-constructible. This is a requirement for using the macro.</li> <li><code>A</code> has private members and is not a derived class. Hence, macro <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code> is used.</li> <li>As <code>B</code> is a derived class, <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code> is not applicable, but <code>NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE</code> must be used.</li> <li>The macro <code>NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE</code> is used <em>inside</em> the class use as <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code>.</li> </ul> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_intrusive/ >NLOHMANN_DEFINE_TYPE_INTRUSIVE / NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT / NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros that can be defined <em>inside</em> a non-derived type.</li> <li><a href=../nlohmann_define_type_non_intrusive/ >NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE / NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT / NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros that can be defined <em>outside</em> a non-derived type.</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 Line truncated
</code></pre></div> <p>Notes:</p> <ul> <li><code>A</code> and <code>B</code> are default-constructible. This is a requirement for using the macro.</li> <li><code>A</code> has private members and is not a derived class. Hence, macro <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code> is used.</li> <li>As <code>B</code> is a derived class, <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code> is not applicable, but <code>NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE</code> must be used.</li> <li>The macro <code>NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE</code> is used <em>inside</em> the class use as <code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code>.</li> </ul> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_intrusive/ >NLOHMANN_DEFINE_TYPE_INTRUSIVE / NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT / NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros that can be defined <em>inside</em> a non-derived type.</li> <li><a href=../nlohmann_define_type_non_intrusive/ >NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE / NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT / NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros that can be defined <em>outside</em> a non-derived type.</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> <li>Added in version 3.12.0.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.Line truncated
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<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(type, member...) </span><span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE(type, member...) </span><span class=c1>// (3)</span>
</code></pre></div> <p>These macros can be used to simplify the serialization/deserialization of types if you want to use a <abbr title="JavaScript Object Notation">JSON</abbr> object as serialization and want to use the member variable names as object keys in that object. The macro is to be defined <strong>inside</strong> the class/struct to create code for. Unlike <a href=../nlohmann_define_type_non_intrusive/ ><code>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE</code></a>, it can access private members. The first parameter is the name of the class/struct, and all remaining parameters name the members.</p> <ol> <li>Will use <a href=../../basic_json/at/ ><code>at</code></a> during deserialization and will throw <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if a key is missing in the <abbr title="JavaScript Object Notation">JSON</abbr> object.</li> <li>Will use <a href=../../basic_json/value/ ><code>value</code></a> during deserialization and fall back to the default value for the respective type of the member variable if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object is missing. The generated <code>from_json()</code> function default constructs an object and uses its values as the defaults when calling the <code>value</code> function.</li> <li>Only defines the serialization. Useful in cases when the type does not have a default constructor and only serialization is required.</li> </ol> <p>Summary:</p> <table> <thead> <tr> <th>Need access to private members</th> <th>Need only serialization</th> <th>Allow missing values when de-serializing</th> <th>macro</th> </tr> </thead> <tbody> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_INTRUSIVE</strong></td> </tr> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT</strong></td> </tr> <tr> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-Line truncated
@@ -291,4 +291,4 @@
<span class=w> </span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>;</span>
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=s>"serialization: "</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_non_intrusive/ >NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for a similar macro that can be defined <em>outside</em> the type.</li> <li><a href=../nlohmann_define_derived_type/ >NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros for derived types</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.9.0.</li> <li>Added in version 3.11.0.</li> <li>Added in version 3.11.3.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_non_intrusive/ >NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for a similar macro that can be defined <em>outside</em> the type.</li> <li><a href=../nlohmann_define_derived_type/ >NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros for derived types</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.9.0.</li> <li>Added in version 3.11.0.</li> <li>Added in version 3.11.3.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/" rel="canonical"><link href=../nlohmann_define_type_intrusive/ rel=prev><link href=../nlohmann_define_type_with_names/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains 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<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(type, member...) </span><span class=c1>// (2)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE(type, member...) </span><span class=c1>// (3)</span>
</code></pre></div> <p>These macros can be used to simplify the serialization/deserialization of types if you want to use a <abbr title="JavaScript Object Notation">JSON</abbr> object as serialization and want to use the member variable names as object keys in that object. The macro is to be defined <strong>outside</strong> the class/struct to create code for, but <strong>inside</strong> its namespace. Unlike <a href=../nlohmann_define_type_intrusive/ ><code>NLOHMANN_DEFINE_TYPE_INTRUSIVE</code></a>, it <strong>cannot</strong> access private members. The first parameter is the name of the class/struct, and all remaining parameters name the members.</p> <ol> <li>Will use <a href=../../basic_json/at/ ><code>at</code></a> during deserialization and will throw <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if a key is missing in the <abbr title="JavaScript Object Notation">JSON</abbr> object.</li> <li>Will use <a href=../../basic_json/value/ ><code>value</code></a> during deserialization and fall back to the default value for the respective type of the member variable if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object is missing. The generated <code>from_json()</code> function default constructs an object and uses its values as the defaults when calling the <code>value</code> function.</li> <li>Only defines the serialization. Useful in cases when the type does not have a default constructor and only serialization is required.</li> </ol> <p>Summary:</p> <table> <thead> <tr> <th>Need access to private members</th> <th>Need only serialization</th> <th>Allow missing values when de-serializing</th> <th>macro</th> </tr> </thead> <tbody> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE</strong></td> </tr> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.326-1.275.75.75 0 0 0-.734.215L12 10.939Z"/></svg></span></div></td> <td><div style="color: green;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m16.28-2.72a.75.75 0 0 0-.018-1.042.75.75 0 0 0-1.042-.018l-5.97 5.97-2.47-2.47a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042l3 3a.75.75 0 0 0 1.06 0Z"/></svg></span></div></td> <td><strong>NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT</strong></td> </tr> <tr> <td><div style="color: red;"><span class=twemoji><svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M1 12C1 5.925 5.925 1 12 1s11 4.925 11 11-4.925 11-11 11S1 18.075 1 12m8.036-4.024a.75.75 0 0 0-1.042.018.75.75 0 0 0-.018 1.042L10.939 12l-2.963 2.963a.749.749 0 0 0 .326 1.275.75.75 0 0 0 .734-.215L12 13.06l2.963 2.964a.75.75 0 0 0 1.061-1.06L13.061 12l2.963-2.964a.749.749 0 0 0-.32Line truncated
@@ -259,4 +259,4 @@
<span class=w> </span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>;</span>
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=s>"serialization: "</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_intrusive/ >NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE</a> for a similar macro that can be defined <em>inside</em> the type.</li> <li><a href=../nlohmann_define_derived_type/ >NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros for derived types</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.9.0.</li> <li>Added in version 3.11.0.</li> <li>Added in version 3.11.3.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_define_type_intrusive/ >NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE</a> for a similar macro that can be defined <em>inside</em> the type.</li> <li><a href=../nlohmann_define_derived_type/ >NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE</a> for similar macros for derived types</li> <li><a href=../../../features/arbitrary_types/ >Arbitrary Type Conversions</a> for an overview.</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.9.0.</li> <li>Added in version 3.11.0.</li> <li>Added in version 3.11.3.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_with_names/" rel="canonical"><link href=../nlohmann_define_type_non_intrusive/ rel=prev><link href=../nlohmann_json_namespace/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_define_type_with_names/" rel="canonical"><link href=../nlohmann_define_type_non_intrusive/ rel=prev><link href=../nlohmann_json_namespace/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#parameters class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__buLine truncated
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES(type, "json_member_name", member...)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES(type, "json_member_name", member...)</span>
<span class=cp>#define NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES(type, "json_member_name", member...)</span>
@@ -108,4 +108,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=s>"deserialization failed: "</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>e</span><span class=p>.</span><span class=n>what</span><span class=p>()</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=w> </span><span class=p>}</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 3.13.0.</li> </ol> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 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</code></pre></div> <p>This macro evaluates to the full name of the <code>nlohmann</code> namespace.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value consists of the root namespace (<code>nlohmann</code>) and an inline ABI namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <p>When the macro is not defined, the library will define it to its default value. Overriding this value has no effect on the library.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example shows how to use <code>NLOHMANN_JSON_NAMESPACE</code> instead of just <code>nlohmann</code>, as well as how to output the value of <code>NLOHMANN_JSON_NAMESPACE</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
@@ -14,4 +14,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>QUOTE</span><span class=p>(</span><span class=n>NLOHMANN_JSON_NAMESPACE</span><span class=p>)</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>nl</span><span class=err>ohma</span><span class=kc>nn</span><span class=p>::</span><span class=err>jso</span><span class=kc>n</span><span class=err>_abi_v</span><span class=mi>3</span><span class=err>_</span><span class=mi>12</span><span class=err>_</span><span class=mi>0</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=httpLine truncated
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=htLine truncated
@@ -1,4 +1,4 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_namespace_begin/" rel="canonical"><link href=../nlohmann_json_namespace/ rel=prev><link href=../nlohmann_json_namespace_no_version/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/nlohmann_json_namespace_begin/" rel="canonical"><link href=../nlohmann_json_namespace/ rel=prev><link href=../nlohmann_json_namespace_no_version/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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<span class=cp>#define NLOHMANN_JSON_NAMESPACE_END </span><span class=cm>/* value */</span><span class=cp> </span><span class=c1>// (2)</span>
</code></pre></div> <p>These macros can be used to open and close the <code>nlohmann</code> namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <ol> <li>Opens the namespace.</li> <li>Closes the namespace.</li> </ol> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default definitions open and close the <code>nlohmann</code> namespace. The precise definition of [<code>NLOHMANN_JSON_NAMESPACE_BEGIN</code>] varies as described <a href=../../../features/namespace/#structure>here</a>.</p> <ol> <li> <p>Default definition of <code>NLOHMANN_JSON_NAMESPACE_BEGIN</code>:</p> <div class=highlight><pre><span></span><code><span class=k>namespace</span><span class=w> </span><span class=nn>nlohmann</span>
<span class=p>{</span>
@@ -40,4 +40,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=p>[</span><span class=mi>1</span><span class=p>,</span><span class=kc>null</span><span class=p>]</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/namespace/ ><code>nlohmann</code> Namespace</a></li> <li><a href=../nlohmann_json_namespace/ >NLOHMANN_JSON_NAMESPACE</a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-sLine truncated
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/namespace/ ><code>nlohmann</code> Namespace</a></li> <li><a href=../nlohmann_json_namespace/ >NLOHMANN_JSON_NAMESPACE</a></li> <li><a href=../nlohmann_json_namespace_no_version/ ><code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.0. Changed inline namespace name in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="mdLine truncated
@@ -1,4 +1,4 @@
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URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmann_json_namespace_no_version class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_NO_VERSION </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo 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6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 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</code></pre></div> <p>If defined to <code>1</code>, the version component is omitted from the inline namespace. See <a href=../../../features/namespace/#structure><code>nlohmann</code> Namespace</a> for details.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The default value is <code>0</code>.</p> <div class=highlight><pre><span></span><code><span class=cp>#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0</span>
</code></pre></div> <p>When the macro is not defined, the library will define it to its default value.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example shows how to use <code>NLOHMANN_JSON_NAMESPACE_NO_VERSION</code> to disable the version component of the inline namespace.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
@@ -14,4 +14,4 @@
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>QUOTE</span><span class=p>(</span><span class=n>NLOHMANN_JSON_NAMESPACE</span><span class=p>)</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>nl</span><span class=err>ohma</span><span class=kc>nn</span><span class=p>::</span><span class=err>jso</span><span class=kc>n</span><span class=err>_abi</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/namespace/ ><code>nlohmann</code> Namespace</a></li> <li><a href=../nlohmann_json_namespace/ ><code>NLOHMANN_JSON_NAMESPACE</code></a></li> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/namespace/ ><code>nlohmann</code> Namespace</a></li> <li><a href=../nlohmann_json_namespace/ ><code>NLOHMANN_JSON_NAMESPACE</code></a></li> <li><a href=../nlohmann_json_namespace_begin/ ><code>NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.11.2.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>By default, enum values are serialized to <abbr title="JavaScript Object Notation">JSON</abbr> as integers. In some cases, this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to <abbr title="JavaScript Object Notation">JSON</abbr>, the later deserialized <abbr title="JavaScript Object Notation">JSON</abbr> data may be undefined or a different enum value than was originally intended.</p> <p>The <code>NLOHMANN_JSON_SERIALIZE_ENUM</code> allows to define a user-defined serialization for every enumerator.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>type</code> (in)</dt> <dd>name of the enum to serialize/deserialize</dd> <dt><code>conversion</code> (in)</dt> <dd>a pair of an enumerator and a <abbr title="JavaScript Object Notation">JSON</abbr> serialization; arbitrary pairs can be given as a comma-separated list</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macro adds two functions to the namespace which take care of the serialization and deserialization:</p> <div class=highlight><pre><span></span><code><span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
<span class=kr>inline</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=n>to_json</span><span class=p>(</span><span class=n>BasicJsonType</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>type</span><span class=o>&amp;</span><span class=w> </span><span class=n>e</span><span class=p>);</span>
<span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
@@ -101,4 +101,4 @@
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=mi>0</span><span class=w> </span><span class=mi>-</span><span class=err>&gt;</span><span class=w> </span><span class=s2>"red"</span>
<span class=s2>"rot"</span><span class=w> </span><span class=mi>-</span><span class=err>&gt;</span><span class=w> </span><span class=mi>0</span>
<span class=s2>"red"</span><span class=w> </span><span class=mi>-</span><span class=err>&gt;</span><span class=w> </span><span class=mi>0</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/enum_conversion/ >Specializing enum conversion</a></li> <li><a href=../nlohmann_json_serialize_enum_strict/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM_STRICT</code></a></li> <li><a href=../json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 3.4.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/enum_conversion/ >Specializing enum conversion</a></li> <li><a href=../nlohmann_json_serialize_enum_strict/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM_STRICT</code></a></li> <li><a href=../json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 3.4.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>By default, enum values are serialized to <abbr title="JavaScript Object Notation">JSON</abbr> as integers. In some cases, this could result in undesired behavior. If an enum is modified or re-ordered after data has been serialized to <abbr title="JavaScript Object Notation">JSON</abbr>, the later deserialized <abbr title="JavaScript Object Notation">JSON</abbr> data may be undefined or a different enum value than was originally intended.</p> <p><code>NLOHMANN_JSON_SERIALIZE_ENUM_STRICT</code> allows to define a user-defined serialization for every enumerator that throws an exception on undefined input.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>type</code> (in)</dt> <dd>name of the enum to serialize/deserialize</dd> <dt><code>conversion</code> (in)</dt> <dd>a pair of an enumerator and a <abbr title="JavaScript Object Notation">JSON</abbr> serialization; arbitrary pairs can be given as a comma-separated list</dd> </dl> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macro adds two functions to the namespace which take care of the serialization and deserialization:</p> <div class=highlight><pre><span></span><code><span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
<span class=kr>inline</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=n>to_json</span><span class=p>(</span><span class=n>BasicJsonType</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>type</span><span class=o>&amp;</span><span class=w> </span><span class=n>e</span><span class=p>);</span>
<span class=k>template</span><span class=o>&lt;</span><span class=k>typename</span><span class=w> </span><span class=nc>BasicJsonType</span><span class=o>&gt;</span>
@@ -148,4 +148,4 @@
<span class=p>}</span>
</code></pre></div> <p>Output: <div class=highlight><pre><span></span><code><span class=err>deserializa</span><span class=kc>t</span><span class=err>io</span><span class=kc>n</span><span class=w> </span><span class=kc>fa</span><span class=err>iled</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=err>jso</span><span class=kc>n</span><span class=err>.excep</span><span class=kc>t</span><span class=err>io</span><span class=kc>n</span><span class=err>.ou</span><span class=kc>t</span><span class=err>_o</span><span class=kc>f</span><span class=err>_ra</span><span class=kc>n</span><span class=err>ge.</span><span class=mi>410</span><span class=p>]</span><span class=w> </span><span class=err>e</span><span class=kc>nu</span><span class=err>m</span><span class=w> </span><span class=err>value</span><span class=w> </span><span class=err>ou</span><span class=kc>t</span><span class=w> </span><span class=err>o</span><span class=kc>f</span><span class=w> </span><span class=err>ra</span><span class=kc>n</span><span class=err>ge</span><span class=w> </span><span class=kc>f</span><span class=err>or</span><span class=w> </span><span class=err>Color</span>
<span class=err>deserializa</span><span class=kc>t</span><span class=err>io</span><span class=kc>n</span><span class=w> </span><span class=kc>fa</span><span class=err>iled</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=err>jso</span><span class=kc>n</span><span class=err>.excep</span><span class=kc>t</span><span class=err>io</span><span class=kc>n</span><span class=err>.ou</span><span class=kc>t</span><span class=err>_o</span><span class=kc>f</span><span class=err>_ra</span><span class=kc>n</span><span class=err>ge.</span><span class=mi>410</span><span class=p>]</span><span class=w> </span><span class=err>e</span><span class=kc>nu</span><span class=err>m</span><span class=w> </span><span class=err>value</span><span class=w> </span><span class=err>ou</span><span class=kc>t</span><span class=w> </span><span class=err>o</span><span class=kc>f</span><span class=w> </span><span class=err>ra</span><span class=kc>n</span><span class=err>ge</span><span class=w> </span><span class=kc>f</span><span class=err>or</span><span class=w> </span><span class=err>Color</span><span class=p>:</span><span class=w> </span><span class=s2>"what"</span>
</code></pre></div></p> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/enum_conversion/ >Specializing enum conversion</a></li> <li><a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a></li> <li><a href=../json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 3.13.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div></p> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../../features/enum_conversion/ >Specializing enum conversion</a></li> <li><a href=../nlohmann_json_serialize_enum/ ><code>NLOHMANN_JSON_SERIALIZE_ENUM</code></a></li> <li><a href=../json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <p>Added in version 3.13.0.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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<span class=cp>#define NLOHMANN_JSON_VERSION_MINOR </span><span class=cm>/* value */</span>
<span class=cp>#define NLOHMANN_JSON_VERSION_PATCH </span><span class=cm>/* value */</span>
</code></pre></div> <p>These macros are defined by the library and contain the version numbers according to <a href="https://semver.org/spec/v2.0.0.html">Semantic Versioning 2.0.0</a>.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>The macros are defined according to the current library version.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <p>The example below shows how <code>NLOHMANN_JSON_VERSION_MAJOR</code>, <code>NLOHMANN_JSON_VERSION_MINOR</code>, and <code>NLOHMANN_JSON_VERSION_PATCH</code> are defined by the library.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
@@ -14,4 +14,4 @@
<span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>NLOHMANN_JSON_VERSION_PATCH</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=err>JSON</span><span class=w> </span><span class=kc>f</span><span class=err>or</span><span class=w> </span><span class=err>Moder</span><span class=kc>n</span><span class=w> </span><span class=err>C++</span><span class=w> </span><span class=err>versio</span><span class=kc>n</span><span class=w> </span><span class=mf>3.12.0</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../basic_json/meta/ >meta</a> - returns version information on the library</li> <li><a href=../json_skip_library_version_check/ >JSON_SKIP_LIBRARY_VERSION_CHECK</a> - skip library version check</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.1.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 9, 2026 07:54:12 UTC">September 9, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../basic_json/meta/ >meta</a> - returns version information on the library</li> <li><a href=../json_skip_library_version_check/ >JSON_SKIP_LIBRARY_VERSION_CHECK</a> - skip library version check</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.1.0.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="September 10, 2026 15:20:48 UTC">September 10, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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