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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=description content="JSON for Modern C++ is a header-only C++11 library that makes JSON a first-class data type."><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/home/architecture/" rel="canonical"><link href=../design_goals/ rel=prev><link href=../customers/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.8.0"><title>Architecture - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.57a0d79d.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.fb2fffe2.min.css><link rel=stylesheet href=../../css/custom.css><link rel=stylesheet href=../../css/brand.css><link rel=stylesheet href=../../css/fig-sax.css><link rel=stylesheet href=../../css/fig-jsonview.css><link rel=stylesheet 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input[/"input&lt;br&gt;(string, stream,&lt;br&gt;iterator range, file)"/]
ia["input adapter"]
lexer["lexer"]
@@ -138,4 +138,4 @@
<span class=k>template</span><span class=o>&lt;</span><span class=k>class</span><span class=w> </span><span class=nc>T</span><span class=o>&gt;</span>
<span class=kt>void</span><span class=w> </span><span class=n>from_json</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>basic_json</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=n>T</span><span class=o>&amp;</span><span class=w> </span><span class=n>t</span><span class=p>);</span>
</code></pre></div> <p>found by argument-dependent lookup. The library defines them for standard types in <code>detail/conversions</code>; users add them for their own types, see <a href=../../features/arbitrary_types/ >Arbitrary Type Conversions</a>. The <a href=../../features/macros/ >serialization macros</a> generate these functions.</p> <h2 id=additional-features>Additional features<a class=headerlink href=#additional-features title="Permanent link">&para;</a></h2> <ul> <li><a href=../../features/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> (class <code>json_pointer</code>) addresses values inside a tree. It is also the basis of <a href=../../features/json_patch/ ><abbr title="JavaScript Object Notation">JSON</abbr> Patch</a>.</li> <li><a href=../../features/binary_formats/ >Binary formats</a> are read by <code>binary_reader</code> and written by <code>binary_writer</code>.</li> <li>A <a href=../../api/basic_json/json_base_class_t/ >custom base class</a> can add members to every <a href=../../api/basic_json/ ><code>basic_json</code></a> value.</li> <li><a href=../../features/macros/ >Serialization macros</a> generate <code>to_json</code> and <code>from_json</code> functions for user-defined types.</li> </ul> <h2 id=details-namespace>Details namespace<a class=headerlink href=#details-namespace title="Permanent link">&para;</a></h2> <p>Namespace <code>nlohmann::detail</code> contains all implementation details. It is not part of the public <abbr title="Application Programming Interface">API</abbr> and may change in any release. Besides the components above, it contains:</p> <ul> <li>type traits to detect the capabilities of user-defined types (<code>detail/meta/type_traits.hpp</code>),</li> <li>backports of C++14/17 features to C++11 (<code>detail/meta/cpp_future.hpp</code>), and</li> <li>helpers such as <code>string_concat</code> and <code>string_escape</code>.</li> </ul> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../api/basic_json/ ><code>basic_json</code></a> - the main class and all its member functions</li> <li><a href=../../api/adl_serializer/ ><code>adl_serializer</code></a> - customization point for type conversions</li> <li><a href=../../api/json_sax/ ><code>json_sax</code></a> - interface of the <abbr title="Simple API for XML">SAX</abbr> parser events</li> <li><a href=../../features/parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> Interface</a> - how to consume parser events without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../../features/json_view/ >Zero-copy <abbr title="JavaScript Object Notation">JSON</abbr> views</a> - the flat node index that backs views and documents</li> <li><a href=../../features/types/template_parameters/ >Template Parameter Requirements</a> - the template parameters of basic_json</li> <li><a href=../../features/serialization/ >Serialization</a> - the output side of the library</li> <li><a href=../../features/namespace/ ><code>nlohmann</code> Namespace</a> - how the library namespace is structured</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="October 28, 2026 19:24:49 UTC">October 28, 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> <nav class="md-footer__inner md-grid" aria-label=Footer> <a href=../design_goals/ class="md-footer__link md-footer__link--prev" aria-label="Previous: Design goals"> <div class="md-footer__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M20 Line truncated
</code></pre></div> <p>found by argument-dependent lookup. The library defines them for standard types in <code>detail/conversions</code>; users add them for their own types, see <a href=../../features/arbitrary_types/ >Arbitrary Type Conversions</a>. The <a href=../../features/macros/ >serialization macros</a> generate these functions.</p> <h2 id=additional-features>Additional features<a class=headerlink href=#additional-features title="Permanent link">&para;</a></h2> <ul> <li><a href=../../features/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> (class <code>json_pointer</code>) addresses values inside a tree. It is also the basis of <a href=../../features/json_patch/ ><abbr title="JavaScript Object Notation">JSON</abbr> Patch</a>.</li> <li><a href=../../features/binary_formats/ >Binary formats</a> are read by <code>binary_reader</code> and written by <code>binary_writer</code>.</li> <li>A <a href=../../api/basic_json/json_base_class_t/ >custom base class</a> can add members to every <a href=../../api/basic_json/ ><code>basic_json</code></a> value.</li> <li><a href=../../features/macros/ >Serialization macros</a> generate <code>to_json</code> and <code>from_json</code> functions for user-defined types.</li> </ul> <h2 id=details-namespace>Details namespace<a class=headerlink href=#details-namespace title="Permanent link">&para;</a></h2> <p>Namespace <code>nlohmann::detail</code> contains all implementation details. It is not part of the public <abbr title="Application Programming Interface">API</abbr> and may change in any release. Besides the components above, it contains:</p> <ul> <li>type traits to detect the capabilities of user-defined types (<code>detail/meta/type_traits.hpp</code>),</li> <li>backports of C++14/17 features to C++11 (<code>detail/meta/cpp_future.hpp</code>), and</li> <li>helpers such as <code>string_concat</code> and <code>string_escape</code>.</li> </ul> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../api/basic_json/ ><code>basic_json</code></a> - the main class and all its member functions</li> <li><a href=../../api/adl_serializer/ ><code>adl_serializer</code></a> - customization point for type conversions</li> <li><a href=../../api/json_sax/ ><code>json_sax</code></a> - interface of the <abbr title="Simple API for XML">SAX</abbr> parser events</li> <li><a href=../../features/parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> Interface</a> - how to consume parser events without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../../features/json_view/ >Zero-copy <abbr title="JavaScript Object Notation">JSON</abbr> views</a> - the flat node index that backs views and documents</li> <li><a href=../../features/types/template_parameters/ >Template Parameter Requirements</a> - the template parameters of basic_json</li> <li><a href=../../features/serialization/ >Serialization</a> - the output side of the library</li> <li><a href=../../features/namespace/ ><code>nlohmann</code> Namespace</a> - how the library namespace is structured</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="November 9, 2026 07:12:00 UTC">November 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> <nav class="md-footer__inner md-grid" aria-label=Footer> <a href=../design_goals/ class="md-footer__link md-footer__link--prev" aria-label="Previous: Design goals"> <div class="md-footer__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M20 Line truncated