deploy: ef1cdb59ac

api/basic_json/to_bjdata.md

@@ -212,4 +212,6 @@ Linear in the size of the JSON value `j`.
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
 - Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
-  array or object was silently skipped, producing invalid BJData.
+  array or object was silently skipped, producing invalid BJData.
+- Writes unsigned integers wider than 64 bits as high-precision numbers since version 3.13.0; previously, they were
+  silently truncated to 64 bits.

api/basic_json/to_bjdata/index.html

@@ -103,4 +103,4 @@
 <span class=w>    </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=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>.o</span><span class=kc>t</span><span class=err>her_error.</span><span class=mi>502</span><span class=p>]</span><span class=w> </span><span class=err>use_</span><span class=kc>t</span><span class=err>ype</span><span class=w> </span><span class=err>requires</span><span class=w> </span><span class=err>use_size</span><span class=w> </span><span class=err>=</span><span class=w> </span><span class=kc>true</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=../from_bjdata/ >from_bjdata</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary JData">BJData</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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> <li><abbr title="Binary JData">BJData</abbr> version parameter (for draft3 binary encoding) added in version 3.12.0.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid <abbr title="Binary JData">BJData</abbr>.</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 6, 2026 05:33:34 UTC">October 6, 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 25.8Line 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=../from_bjdata/ >from_bjdata</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary JData">BJData</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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> <li><abbr title="Binary JData">BJData</abbr> version parameter (for draft3 binary encoding) added in version 3.12.0.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid <abbr title="Binary JData">BJData</abbr>.</li> <li>Writes unsigned integers wider than 64 bits as high-precision numbers since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, they were silently truncated to 64 bits.</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 21, 2026 08:36:31 UTC">October 21, 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-Line truncated

api/basic_json/to_bjdata/index.md

@@ -189,3 +189,4 @@ Output:
 - BJData version parameter (for draft3 binary encoding) added in version 3.12.0.
 - Added `error_handler` parameter in version 3.13.0 unreleased. Its default, `keep`, writes the bytes of a string or object key that is not valid UTF-8 unchanged, as before; `strict` (the default if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled) throws `type_error.316`.
 - Throws `type_error.321` for a discarded value since version 3.13.0 unreleased; previously, a discarded value nested in an array or object was silently skipped, producing invalid BJData.
+- Writes unsigned integers wider than 64 bits as high-precision numbers since version 3.13.0 unreleased; previously, they were silently truncated to 64 bits.

api/basic_json/to_bon8.md

@@ -37,8 +37,9 @@ With (2), the bytes written before the exception remain in the output adapter.
 
 ## Exceptions
 
-- Throws [out_of_range.407](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains an unsigned integer
-  above 9223372036854775807, which BON8 cannot represent
+- Throws [out_of_range.407](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains an integer outside
+  the range of int64 (an unsigned integer above 9223372036854775807, or, with a number type wider than 64 bits, any
+  integer beyond int64), which BON8 cannot represent
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if `j` contains a string that is not
   valid UTF-8
 - Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is

api/basic_json/to_bon8/index.html

@@ -4,7 +4,7 @@
 <span class=c1>// (2)</span>
 <span class=k>static</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=nf>to_bon8</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>detail</span><span class=o>::</span><span class=n>output_adapter</span><span class=o>&lt;</span><span class=n>std</span><span class=o>::</span><span class=kt>uint8_t</span><span class=o>&gt;</span><span class=w> </span><span class=n>o</span><span class=p>);</span>
 <span class=k>static</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=nf>to_bon8</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>detail</span><span class=o>::</span><span class=n>output_adapter</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=w> </span><span class=n>o</span><span class=p>);</span>
-</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the <abbr title="Binary Object Notation 8">BON8</abbr> (Binary Object Notation 8) serialization format. <abbr title="Binary Object Notation 8">BON8</abbr> is a compact binary serialization format that stores strings as <abbr title="Unicode Transformation Format">UTF</abbr>-8 without a length prefix.</p> <ol> <li>Returns a byte vector containing the <abbr title="Binary Object Notation 8">BON8</abbr> serialization.</li> <li>Writes the <abbr title="Binary Object Notation 8">BON8</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/bon8/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Binary Object Notation 8">BON8</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>, which is never modified. With (2), the bytes written before the exception remain in the output adapter.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range407>out_of_range.407</a> if <code>j</code> contains an unsigned integer above 9223372036854775807, which <abbr title="Binary Object Notation 8">BON8</abbr> cannot represent</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if <code>j</code> contains a string that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to BON8"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: serialize a <abbr title="JavaScript Object Notation">JSON</abbr> value to <abbr title="Binary Object Notation 8">BON8</abbr></summary> <p>The example shows the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in <abbr title="Binary Object Notation 8">BON8</abbr> format.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
+</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the <abbr title="Binary Object Notation 8">BON8</abbr> (Binary Object Notation 8) serialization format. <abbr title="Binary Object Notation 8">BON8</abbr> is a compact binary serialization format that stores strings as <abbr title="Unicode Transformation Format">UTF</abbr>-8 without a length prefix.</p> <ol> <li>Returns a byte vector containing the <abbr title="Binary Object Notation 8">BON8</abbr> serialization.</li> <li>Writes the <abbr title="Binary Object Notation 8">BON8</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/bon8/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Binary Object Notation 8">BON8</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>, which is never modified. With (2), the bytes written before the exception remain in the output adapter.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range407>out_of_range.407</a> if <code>j</code> contains an integer outside the range of int64 (an unsigned integer above 9223372036854775807, or, with a number type wider than 64 bits, any integer beyond int64), which <abbr title="Binary Object Notation 8">BON8</abbr> cannot represent</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if <code>j</code> contains a string that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to BON8"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: serialize a <abbr title="JavaScript Object Notation">JSON</abbr> value to <abbr title="Binary Object Notation 8">BON8</abbr></summary> <p>The example shows the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in <abbr title="Binary Object Notation 8">BON8</abbr> format.</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;iomanip&gt;</span>
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
@@ -50,4 +50,4 @@
 <span class=w>    </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=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>.</span><span class=kc>t</span><span class=err>ype_error.</span><span class=mi>316</span><span class=p>]</span><span class=w> </span><span class=err>i</span><span class=kc>n</span><span class=err>valid</span><span class=w> </span><span class=err>UTF</span><span class=mi>-8</span><span class=w> </span><span class=err>by</span><span class=kc>te</span><span class=w> </span><span class=err>a</span><span class=kc>t</span><span class=w> </span><span class=err>i</span><span class=kc>n</span><span class=err>dex</span><span class=w> </span><span class=mi>0</span><span class=p>:</span><span class=w> </span><span class=mi>0</span><span class=err>xFF</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=../from_bon8/ >from_bon8</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary Object Notation 8">BON8</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</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 11, 2026 06:22:00 UTC">October 11, 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=../from_bon8/ >from_bon8</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary Object Notation 8">BON8</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</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 21, 2026 08:36:31 UTC">October 21, 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/" tLine truncated

api/basic_json/to_bon8/index.md

@@ -33,7 +33,7 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Exceptions
 
-- Throws [out_of_range.407](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range407) if `j` contains an unsigned integer above 9223372036854775807, which BON8 cannot represent
+- Throws [out_of_range.407](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range407) if `j` contains an integer outside the range of int64 (an unsigned integer above 9223372036854775807, or, with a number type wider than 64 bits, any integer beyond int64), which BON8 cannot represent
 - Throws [type_error.316](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) if `j` contains a string that is not valid UTF-8
 - Throws [type_error.321](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error321) if `j` or a value nested in it is discarded; example: `"cannot serialize discarded value to BON8"`
 

api/basic_json/to_bson.md

@@ -47,6 +47,10 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 - Throws [`type_error.317`](../../home/exceptions.md#jsonexceptiontype_error317) if the top-level type of the JSON value
   is not an object; example: `"to serialize to BSON, top-level type must be object, but is string"`
+- Throws [`out_of_range.407`](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains a signed integer
+  outside the range of int64 or an unsigned integer outside the range of uint64, which is only possible with a number
+  type wider than 64 bits; example:
+  `"integer number 9223372036854775808 cannot be represented by BSON as it does not fit int64"`
 - Throws [`out_of_range.409`](../../home/exceptions.md#jsonexceptionout_of_range409) if a key in the JSON object contains
   a null byte (code point U+0000); example: `"BSON key cannot contain code point U+0000 (at byte 2)"`
 - Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a document, array,
@@ -166,3 +170,5 @@ pass before anything is written.
   that is not valid UTF-8 unchanged, as before; `strict` (the default if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316` before anything
   is written.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0; previously, integers of a
+  number type wider than 64 bits were silently truncated.

api/basic_json/to_bson/index.html

@@ -7,7 +7,7 @@
 <span class=w>                    </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
 <span class=k>static</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=nf>to_bson</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>detail</span><span class=o>::</span><span class=n>output_adapter</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=w> </span><span class=n>o</span><span class=p>,</span>
 <span class=w>                    </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
-</code></pre></div> <p><abbr title="Binary JSON">BSON</abbr> (Binary <abbr title="JavaScript Object Notation">JSON</abbr>) is a binary format in which zero or more ordered key/value pairs are stored as a single entity (a so-called document).</p> <ol> <li>Returns a byte vector containing the <abbr title="Binary JSON">BSON</abbr> serialization.</li> <li>Writes the <abbr title="Binary JSON">BSON</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/bson/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_bson</code> did before this parameter was added; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. If <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled, the default is <code>strict</code> instead.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Binary JSON">BSON</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error317><code>type_error.317</code></a> if the top-level type of the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an object; example: <code>"to serialize to BSON, top-level type must be object, but is string"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range409><code>out_of_range.409</code></a> if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object contains a null byte (code point U+0000); example: <code>"BSON key cannot contain code point U+0000 (at byte 2)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range412><code>out_of_range.412</code></a> if the length of a document, array, string, or binary value exceeds the range of the 32-bit <abbr title="Binary JSON">BSON</abbr> length field; example: <code>"BSON length 2147483661 exceeds maximum of 2147483647"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range415><code>out_of_range.415</code></a> if the subtype of a binary value exceeds 255, the maximum of the <abbr title="Binary JSON">BSON</abbr> binary subtype; example: <code>"subtype 70000 is too large for the BSON binary subtype (max 255)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code> (the default only if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled)</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if a value nested in <code>j</code> is discarded (the top-level value itself is covered by <code>type_error.317</code> above, since it must be an object); example: <code>"cannot serialize discarded value to BSON"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>. The length prefixes of all nested documents and arrays are computed in one pass before anything is written.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: serialize a <abbr title="JavaScript Object Notation">JSON</abbr> value to <abbr title="Binary JSON">BSON</abbr></summary> <p>The example shows the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in <abbr title="Binary JSON">BSON</abbr> format.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;ioLine truncated
+</code></pre></div> <p><abbr title="Binary JSON">BSON</abbr> (Binary <abbr title="JavaScript Object Notation">JSON</abbr>) is a binary format in which zero or more ordered key/value pairs are stored as a single entity (a so-called document).</p> <ol> <li>Returns a byte vector containing the <abbr title="Binary JSON">BSON</abbr> serialization.</li> <li>Writes the <abbr title="Binary JSON">BSON</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/bson/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_bson</code> did before this parameter was added; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. If <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled, the default is <code>strict</code> instead.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Binary JSON">BSON</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error317><code>type_error.317</code></a> if the top-level type of the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an object; example: <code>"to serialize to BSON, top-level type must be object, but is string"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range407><code>out_of_range.407</code></a> if <code>j</code> contains a signed integer outside the range of int64 or an unsigned integer outside the range of uint64, which is only possible with a number type wider than 64 bits; example: <code>"integer number 9223372036854775808 cannot be represented by BSON as it does not fit int64"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range409><code>out_of_range.409</code></a> if a key in the <abbr title="JavaScript Object Notation">JSON</abbr> object contains a null byte (code point U+0000); example: <code>"BSON key cannot contain code point U+0000 (at byte 2)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range412><code>out_of_range.412</code></a> if the length of a document, array, string, or binary value exceeds the range of the 32-bit <abbr title="Binary JSON">BSON</abbr> length field; example: <code>"BSON length 2147483661 exceeds maximum of 2147483647"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range415><code>out_of_range.415</code></a> if the subtype of a binary value exceeds 255, the maximum of the <abbr title="Binary JSON">BSON</abbr> binary subtype; example: <code>"subtype 70000 is too large for the BSON binary subtype (max 255)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code> (the default only if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled)</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if a value nested in <code>j</code> is discarded (the top-level value itself is covered by <code>type_error.317</code> above, since it must be an object); example: <code>"cannot serialize discarded value to BSON"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>. The length prefixes of all nested documents and arrays are computed in one pass before anything is written.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: seLine truncated
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iomanip&gt;</span>
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
@@ -54,4 +54,4 @@
 <span class=w>    </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=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>409</span><span class=p>]</span><span class=w> </span><span class=err>BSON</span><span class=w> </span><span class=err>key</span><span class=w> </span><span class=err>ca</span><span class=kc>nn</span><span class=err>o</span><span class=kc>t</span><span class=w> </span><span class=err>co</span><span class=kc>nta</span><span class=err>i</span><span class=kc>n</span><span class=w> </span><span class=err>code</span><span class=w> </span><span class=err>poi</span><span class=kc>nt</span><span class=w> </span><span class=err>U+</span><span class=mi>0000</span><span class=w> </span><span class=err>(a</span><span class=kc>t</span><span class=w> </span><span class=err>by</span><span class=kc>te</span><span class=w> </span><span class=mi>2</span><span class=err>)</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=../from_bson/ >from_bson</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary JSON">BSON</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 3.4.0.</li> <li>Throws <code>out_of_range.412</code> and <code>out_of_range.415</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Linear in the size of <code>j</code>, and no longer limited by the call stack for deeply nested values, since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li><code>out_of_range.415</code> is now detected before anything is written, like the other exceptions above, since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Throws <code>type_error.321</code> for a discarded value nested in <code>j</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, it was silently skipped, producing a document whose declared size did not match what was actually written.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code> before anything is written.</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 6, 2026 05:33:34 UTC">October 6, 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 LiLine 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=../from_bson/ >from_bson</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Binary JSON">BSON</abbr> format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 3.4.0.</li> <li>Throws <code>out_of_range.412</code> and <code>out_of_range.415</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Linear in the size of <code>j</code>, and no longer limited by the call stack for deeply nested values, since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li><code>out_of_range.415</code> is now detected before anything is written, like the other exceptions above, since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Throws <code>type_error.321</code> for a discarded value nested in <code>j</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, it was silently skipped, producing a document whose declared size did not match what was actually written.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code> before anything is written.</li> <li>Throws <code>out_of_range.407</code> for integers that do not fit 64 bits since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, integers of a number type wider than 64 bits were silently truncated.</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 21, 2026 08:36:31 UTC">October 21, 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; 201Line truncated

api/basic_json/to_bson/index.md

@@ -39,6 +39,7 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 ## Exceptions
 
 - Throws [`type_error.317`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error317) if the top-level type of the JSON value is not an object; example: `"to serialize to BSON, top-level type must be object, but is string"`
+- Throws [`out_of_range.407`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range407) if `j` contains a signed integer outside the range of int64 or an unsigned integer outside the range of uint64, which is only possible with a number type wider than 64 bits; example: `"integer number 9223372036854775808 cannot be represented by BSON as it does not fit int64"`
 - Throws [`out_of_range.409`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range409) if a key in the JSON object contains a null byte (code point U+0000); example: `"BSON key cannot contain code point U+0000 (at byte 2)"`
 - Throws [`out_of_range.412`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range412) if the length of a document, array, string, or binary value exceeds the range of the 32-bit BSON length field; example: `"BSON length 2147483661 exceeds maximum of 2147483647"`
 - Throws [`out_of_range.415`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range415) if the subtype of a binary value exceeds 255, the maximum of the BSON binary subtype; example: `"subtype 70000 is too large for the BSON binary subtype (max 255)"`
@@ -139,3 +140,4 @@ Output:
 - `out_of_range.415` is now detected before anything is written, like the other exceptions above, since version 3.13.0 unreleased.
 - Throws `type_error.321` for a discarded value nested in `j` since version 3.13.0 unreleased; previously, it was silently skipped, producing a document whose declared size did not match what was actually written.
 - Added `error_handler` parameter in version 3.13.0 unreleased. Its default, `keep`, writes the bytes of a string or object key that is not valid UTF-8 unchanged, as before; `strict` (the default if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled) throws `type_error.316` before anything is written.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0 unreleased; previously, integers of a number type wider than 64 bits were silently truncated.

api/basic_json/to_cbor.md

@@ -46,6 +46,9 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Exceptions
 
+- Throws [`out_of_range.407`](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains an integer
+  outside [-2^64, 2^64-1], which is only possible with a number type wider than 64 bits; example:
+  `"integer number 18446744073709551616 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]"`
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if a string or object key in `j` is
   not valid UTF-8 and `error_handler` is `strict` (the default only if
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled)
@@ -113,3 +116,5 @@ Linear in the size of the JSON value `j`.
   [`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
 - Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
   array or object was silently skipped, producing invalid CBOR.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0; previously, integers of a
+  number type wider than 64 bits were silently truncated.

api/basic_json/to_cbor/index.html

@@ -7,7 +7,7 @@
 <span class=w>                     </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
 <span class=k>static</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=nf>to_cbor</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>detail</span><span class=o>::</span><span class=n>output_adapter</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=w> </span><span class=n>o</span><span class=p>,</span>
 <span class=w>                     </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
-</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the <abbr title="Concise Binary Object Representation">CBOR</abbr> (Concise Binary Object Representation) serialization format. <abbr title="Concise Binary Object Representation">CBOR</abbr> is a binary serialization format that aims to be more compact than <abbr title="JavaScript Object Notation">JSON</abbr> itself, yet more efficient to parse.</p> <ol> <li>Returns a byte vector containing the <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization.</li> <li>Writes the <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/cbor/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_cbor</code> did before this parameter was added; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. If <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled, the default is <code>strict</code> instead.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Concise Binary Object Representation">CBOR</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key in <code>j</code> is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code> (the default only if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled)</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to CBOR"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</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 the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in <abbr title="Concise Binary Object Representation">CBOR</abbr> format.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
+</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the <abbr title="Concise Binary Object Representation">CBOR</abbr> (Concise Binary Object Representation) serialization format. <abbr title="Concise Binary Object Representation">CBOR</abbr> is a binary serialization format that aims to be more compact than <abbr title="JavaScript Object Notation">JSON</abbr> itself, yet more efficient to parse.</p> <ol> <li>Returns a byte vector containing the <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization.</li> <li>Writes the <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/cbor/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_cbor</code> did before this parameter was added; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. If <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled, the default is <code>strict</code> instead.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li><abbr title="Concise Binary Object Representation">CBOR</abbr> serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range407><code>out_of_range.407</code></a> if <code>j</code> contains an integer outside [-2^64, 2^64-1], which is only possible with a number type wider than 64 bits; example: <code>"integer number 18446744073709551616 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key in <code>j</code> is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code> (the default only if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled)</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to CBOR"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</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 the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in <abbr title="Concise Binary Object Representation">CBOR</abbr> format.</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;iomanip&gt;</span>
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
@@ -30,4 +30,4 @@
 <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>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>0</span><span class=err>xa</span><span class=mi>2</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>67</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>63</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>6</span><span class=kc>f</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>6</span><span class=err>d</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>70</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>61</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>63</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>74</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=kc>f</span><span class=mi>5</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>66</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>73</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>63</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>68</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>65</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>6</span><span class=err>d</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>61</span><span class=w> </span><span class=mi>0</span><span class=err>x</span><span class=mi>00</span><span class=w> </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=../from_cbor/ >from_cbor</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Concise Binary Object Representation">CBOR</abbr> format</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 2.0.9.</li> <li>Compact representation of floating-point numbers added in version 3.8.0.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid <abbr title="Concise Binary Object Representation">CBOR</abbr>.</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 6, 2026 05:33:34 UTC">October 6, 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.Line 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=../from_cbor/ >from_cbor</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in <abbr title="Concise Binary Object Representation">CBOR</abbr> format</li> <li><a href=../to_msgpack/ >to_msgpack</a> create a MessagePack serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 2.0.9.</li> <li>Compact representation of floating-point numbers added in version 3.8.0.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before; <code>strict</code> (the default if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled) throws <code>type_error.316</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid <abbr title="Concise Binary Object Representation">CBOR</abbr>.</li> <li>Throws <code>out_of_range.407</code> for integers that do not fit 64 bits since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, integers of a number type wider than 64 bits were silently truncated.</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 21, 2026 08:36:31 UTC">October 21, 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-Line truncated

api/basic_json/to_cbor/index.md

@@ -38,6 +38,7 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Exceptions
 
+- Throws [`out_of_range.407`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range407) if `j` contains an integer outside [-2^64, 2^64-1], which is only possible with a number type wider than 64 bits; example: `"integer number 18446744073709551616 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]"`
 - Throws [type_error.316](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) if a string or object key in `j` is not valid UTF-8 and `error_handler` is `strict` (the default only if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled)
 - Throws [type_error.321](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error321) if `j` or a value nested in it is discarded; example: `"cannot serialize discarded value to CBOR"`
 
@@ -97,3 +98,4 @@ Output:
 - Compact representation of floating-point numbers added in version 3.8.0.
 - Added `error_handler` parameter in version 3.13.0 unreleased. Its default, `keep`, writes the bytes of a string or object key that is not valid UTF-8 unchanged, as before; `strict` (the default if [`JSON_STRICT_BINARY_UTF8`](https://json.nlohmann.me/api/macros/json_strict_binary_utf8/index.md) is enabled) throws `type_error.316`.
 - Throws `type_error.321` for a discarded value since version 3.13.0 unreleased; previously, a discarded value nested in an array or object was silently skipped, producing invalid CBOR.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0 unreleased; previously, integers of a number type wider than 64 bits were silently truncated.

api/basic_json/to_msgpack.md

@@ -46,6 +46,9 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Exceptions
 
+- Throws [`out_of_range.407`](../../home/exceptions.md#jsonexceptionout_of_range407) if `j` contains an integer
+  outside [-2^63, 2^64-1], which is only possible with a number type wider than 64 bits; example:
+  `"integer number 18446744073709551616 cannot be represented by MessagePack as it does not fit [-2^63, 2^64-1]"`
 - Throws [`out_of_range.412`](../../home/exceptions.md#jsonexceptionout_of_range412) if the length of a string, binary
   value, array, or object exceeds 4294967295, the maximum MessagePack can store; example:
   `"MessagePack length 4294967296 exceeds maximum of 4294967295"`
@@ -156,3 +159,5 @@ Linear in the size of the JSON value `j`.
   `number_unsigned_t`.
 - Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
   array or object was silently skipped, producing invalid MessagePack.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0; previously, integers of a
+  number type wider than 64 bits were silently truncated.

api/basic_json/to_msgpack/index.html

@@ -7,7 +7,7 @@
 <span class=w>                       </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
 <span class=k>static</span><span class=w> </span><span class=kt>void</span><span class=w> </span><span class=nf>to_msgpack</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>detail</span><span class=o>::</span><span class=n>output_adapter</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=w> </span><span class=n>o</span><span class=p>,</span>
 <span class=w>                       </span><span class=k>const</span><span class=w> </span><span class=n>error_handler_t</span><span class=w> </span><span class=n>error_handler</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>error_handler_t</span><span class=o>::</span><span class=n>keep</span><span class=p>);</span>
-</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the MessagePack serialization format. MessagePack is a binary serialization format that aims to be more compact than <abbr title="JavaScript Object Notation">JSON</abbr> itself, yet more efficient to parse.</p> <ol> <li>Returns a byte vector containing the MessagePack serialization.</li> <li>Writes the MessagePack serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/messagepack/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_msgpack</code> did before this parameter was added and as the MessagePack specification allows; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. Unlike the other binary writers, the default stays <code>keep</code> even if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li>MessagePack serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range412><code>out_of_range.412</code></a> if the length of a string, binary value, array, or object exceeds 4294967295, the maximum MessagePack can store; example: <code>"MessagePack length 4294967296 exceeds maximum of 4294967295"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range415><code>out_of_range.415</code></a> if the subtype of a binary value exceeds 255, the maximum of the MessagePack ext type; example: <code>"subtype 70000 is too large for the MessagePack ext type (max 255)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key in <code>j</code> is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to MessagePack"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: serialize a <abbr title="JavaScript Object Notation">JSON</abbr> value to MessagePack</summary> <p>The example shows the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in MessagePack format.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
+</code></pre></div> <p>Serializes a given <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code> to a byte vector using the MessagePack serialization format. MessagePack is a binary serialization format that aims to be more compact than <abbr title="JavaScript Object Notation">JSON</abbr> itself, yet more efficient to parse.</p> <ol> <li>Returns a byte vector containing the MessagePack serialization.</li> <li>Writes the MessagePack serialization to an output adapter.</li> </ol> <p>The exact mapping and its limitations are described on a <a href=../../../features/binary_formats/messagepack/ >dedicated page</a>.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>j</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> value to serialize</dd> <dt><code>o</code> (in)</dt> <dd>output adapter to write serialization to</dd> <dt><code>error_handler</code> (in)</dt> <dd>how to treat a string or object key in <code>j</code> that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8; see <a href=../error_handler_t/ ><code>error_handler_t</code></a>. The default, <code>keep</code>, writes the ill-formed bytes to the output as is, as every version of <code>to_msgpack</code> did before this parameter was added and as the MessagePack specification allows; <code>strict</code> throws; <code>replace</code>/<code>ignore</code> sanitize it the same way <a href=../dump/ ><code>dump</code></a> would. Unlike the other binary writers, the default stays <code>keep</code> even if <a href=../../macros/json_strict_binary_utf8/ ><code>JSON_STRICT_BINARY_UTF8</code></a> is enabled.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li>MessagePack serialization as a byte vector</li> <li>(none)</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes in the <abbr title="JavaScript Object Notation">JSON</abbr> value.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range407><code>out_of_range.407</code></a> if <code>j</code> contains an integer outside [-2^63, 2^64-1], which is only possible with a number type wider than 64 bits; example: <code>"integer number 18446744073709551616 cannot be represented by MessagePack as it does not fit [-2^63, 2^64-1]"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range412><code>out_of_range.412</code></a> if the length of a string, binary value, array, or object exceeds 4294967295, the maximum MessagePack can store; example: <code>"MessagePack length 4294967296 exceeds maximum of 4294967295"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range415><code>out_of_range.415</code></a> if the subtype of a binary value exceeds 255, the maximum of the MessagePack ext type; example: <code>"subtype 70000 is too large for the MessagePack ext type (max 255)"</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error316>type_error.316</a> if a string or object key in <code>j</code> is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 and <code>error_handler</code> is <code>strict</code></li> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error321>type_error.321</a> if <code>j</code> or a value nested in it is discarded; example: <code>"cannot serialize discarded value to MessagePack"</code></li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in the size of the <abbr title="JavaScript Object Notation">JSON</abbr> value <code>j</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: serialize a <abbr title="JavaScript Object Notation">JSON</abbr> value to MessagePack</summary> <p>The example shows the serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value to a byte vector in MessagePack format.</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;iomanip&gt;</span>
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
@@ -51,4 +51,4 @@
 <span class=w>    </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=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>415</span><span class=p>]</span><span class=w> </span><span class=err>sub</span><span class=kc>t</span><span class=err>ype</span><span class=w> </span><span class=mi>300</span><span class=w> </span><span class=err>is</span><span class=w> </span><span class=kc>t</span><span class=err>oo</span><span class=w> </span><span class=err>large</span><span class=w> </span><span class=kc>f</span><span class=err>or</span><span class=w> </span><span class=kc>t</span><span class=err>he</span><span class=w> </span><span class=err>MessagePack</span><span class=w> </span><span class=err>ex</span><span class=kc>t</span><span class=w> </span><span class=kc>t</span><span class=err>ype</span><span class=w> </span><span class=err>(max</span><span class=w> </span><span class=mi>255</span><span class=err>)</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=../from_msgpack/ >from_msgpack</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in MessagePack format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 2.0.9.</li> <li>Throws <code>out_of_range.412</code> and <code>out_of_range.415</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before.</li> <li>Fixed in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span> to serialize <code>number_integer_t</code>/<code>number_unsigned_t</code> pairs of different width correctly; before, integers could be serialized with the wrong value if <code>number_integer_t</code> was narrower than <code>number_unsigned_t</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid MessagePack.</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 6, 2026 05:33:34 UTC">October 6, 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 2.3m44.2Line 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=../from_msgpack/ >from_msgpack</a> create a <abbr title="JavaScript Object Notation">JSON</abbr> value from an input in MessagePack format</li> <li><a href=../to_cbor/ >to_cbor</a> create a <abbr title="Concise Binary Object Representation">CBOR</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bson/ >to_bson</a> create a <abbr title="Binary JSON">BSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_ubjson/ >to_ubjson</a> create a <abbr title="Universal Binary JSON">UBJSON</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bjdata/ >to_bjdata</a> create a <abbr title="Binary JData">BJData</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</li> <li><a href=../to_bon8/ >to_bon8</a> create a <abbr title="Binary Object Notation 8">BON8</abbr> serialization of a <abbr title="JavaScript Object Notation">JSON</abbr> value</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 2.0.9.</li> <li>Throws <code>out_of_range.412</code> and <code>out_of_range.415</code> since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> <li>Added <code>error_handler</code> parameter in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Its default, <code>keep</code>, writes the bytes of a string or object key that is not valid <abbr title="Unicode Transformation Format">UTF</abbr>-8 unchanged, as before.</li> <li>Fixed in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span> to serialize <code>number_integer_t</code>/<code>number_unsigned_t</code> pairs of different width correctly; before, integers could be serialized with the wrong value if <code>number_integer_t</code> was narrower than <code>number_unsigned_t</code>.</li> <li>Throws <code>type_error.321</code> for a discarded value since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, a discarded value nested in an array or object was silently skipped, producing invalid MessagePack.</li> <li>Throws <code>out_of_range.407</code> for integers that do not fit 64 bits since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>; previously, integers of a number type wider than 64 bits were silently truncated.</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 21, 2026 08:36:31 UTC">October 21, 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.comLine truncated

api/basic_json/to_msgpack/index.md

@@ -38,6 +38,7 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
 
 ## Exceptions
 
+- Throws [`out_of_range.407`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range407) if `j` contains an integer outside [-2^63, 2^64-1], which is only possible with a number type wider than 64 bits; example: `"integer number 18446744073709551616 cannot be represented by MessagePack as it does not fit [-2^63, 2^64-1]"`
 - Throws [`out_of_range.412`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range412) if the length of a string, binary value, array, or object exceeds 4294967295, the maximum MessagePack can store; example: `"MessagePack length 4294967296 exceeds maximum of 4294967295"`
 - Throws [`out_of_range.415`](https://json.nlohmann.me/home/exceptions/#jsonexceptionout_of_range415) if the subtype of a binary value exceeds 255, the maximum of the MessagePack ext type; example: `"subtype 70000 is too large for the MessagePack ext type (max 255)"`
 - Throws [type_error.316](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error316) if a string or object key in `j` is not valid UTF-8 and `error_handler` is `strict`
@@ -133,3 +134,4 @@ Output:
 - Added `error_handler` parameter in version 3.13.0 unreleased. Its default, `keep`, writes the bytes of a string or object key that is not valid UTF-8 unchanged, as before.
 - Fixed in version 3.13.0 unreleased to serialize `number_integer_t`/`number_unsigned_t` pairs of different width correctly; before, integers could be serialized with the wrong value if `number_integer_t` was narrower than `number_unsigned_t`.
 - Throws `type_error.321` for a discarded value since version 3.13.0 unreleased; previously, a discarded value nested in an array or object was silently skipped, producing invalid MessagePack.
+- Throws `out_of_range.407` for integers that do not fit 64 bits since version 3.13.0 unreleased; previously, integers of a number type wider than 64 bits were silently truncated.

api/macros/json_disable_unlocked_file_io.md

@@ -10,6 +10,9 @@ earlier, instead of locking the file once and reading it with the unlocked stdio
 It does not change any result: values, exceptions, and the position of the file after parsing are the same either way.
 Only the speed and the locking of the file differ (see the notes on locking below).
 
+Builds with MemorySanitizer use `std::fgetc` automatically, because the inline `getc_unlocked` of glibc reads the stdio
+buffer directly, which glibc (not instrumented) filled, and MemorySanitizer would report it as uninitialized.
+
 ## Default definition
 
 The default value is `0`: the file is locked once and read with the unlocked stdio functions where they are available.

api/macros/json_disable_unlocked_file_io/index.html

@@ -1,5 +1,5 @@
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-</code></pre></div> <p>When defined to <code>1</code>, parsing from a <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> reads every character with <code>std::fgetc</code>, as in version 3.12.0 and earlier, instead of locking the file once and reading it with the unlocked stdio functions.</p> <p>It does not change any result: values, exceptions, and the position of the file after parsing are the same either way. Only the speed and the locking of the file differ (see the notes on locking below).</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>: the file is locked once and read with the unlocked stdio functions where they are available.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_UNLOCKED_FILE_IO 0</span>
+</code></pre></div> <p>When defined to <code>1</code>, parsing from a <code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> reads every character with <code>std::fgetc</code>, as in version 3.12.0 and earlier, instead of locking the file once and reading it with the unlocked stdio functions.</p> <p>It does not change any result: values, exceptions, and the position of the file after parsing are the same either way. Only the speed and the locking of the file differ (see the notes on locking below).</p> <p>Builds with MemorySanitizer use <code>std::fgetc</code> automatically, because the inline <code>getc_unlocked</code> of glibc reads the stdio buffer directly, which glibc (not instrumented) filled, and MemorySanitizer would report it as uninitialized.</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>: the file is locked once and read with the unlocked stdio functions where they are available.</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_DISABLE_UNLOCKED_FILE_IO 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>The C standard library makes every <code>std::fgetc</code> call thread-safe by locking and unlocking the <code>FILE</code> object. When parsing from a <code>FILE*</code>, the parser reads one character at a time, so this happens for every character of the input.</p> <p>Instead, the parser locks the file once when parsing starts and unlocks it when parsing ends - also when an exception is thrown - and reads the characters in between without locking:</p> <table> <thead> <tr> <th>C library</th> <th>functions</th> </tr> </thead> <tbody> <tr> <td>glibc (Linux), Apple (macOS, iOS), Android, FreeBSD, NetBSD, OpenBSD, DragonFly BSD</td> <td><code>flockfile</code>, <code>getc_unlocked</code>, <code>funlockfile</code> (POSIX)</td> </tr> <tr> <td>Microsoft (<abbr title="Microsoft Visual C++">MSVC</abbr>, clang-cl)</td> <td><code>_lock_file</code>, <code>_fgetc_nolock</code>, <code>_unlock_file</code></td> </tr> <tr> <td>others (e.g., musl, MinGW, newlib)</td> <td><code>std::fgetc</code>, as before</td> </tr> </tbody> </table> <p>This makes parsing from a <code>FILE*</code> 3 to 4 times as fast with the Apple C library and 1.1 to 1.3 times as fast with glibc, whose locking is cheaper. The binary formats (<a href=../../basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../basic_json/from_msgpack/ ><code>from_msgpack</code></a>, ...) read from a <code>FILE*</code> the same way.</p> </div> <div class="admonition note"> <p class=admonition-title>Locking</p> <p>While a value is parsed from a <code>FILE*</code>, the parsing thread holds the file's lock. The lock is recursive, so the parsing thread itself - for instance, a <a href=../../json_sax/ ><abbr title="Simple API for XML">SAX</abbr></a> handler or a <a href=../../basic_json/parser_callback_t/ >parser callback</a> - can keep using the file with stdio functions such as <code>std::ftell</code>. Other threads that use the same <code>FILE</code> object wait until the parser is done. Before, they could interleave their reads with the parser's, which made the parsed input unpredictable anyway.</p> <p>A program in which a <abbr title="Simple API for XML">SAX</abbr> handler or parser callback waits for <strong>another</strong> thread that uses the <strong>same</strong> <code>FILE</code> object would deadlock. Define the macro to <code>1</code> for such programs.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The value of this macro is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_dufio</code>), resulting in distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.</p> </div> <div class="admonition note"> <p class=admonition-title>Other inputs</p> <p>Reading from a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> is not affected by this macro; see <a href=../json_disable_stream_bulk_scan/ ><code>JSON_DISABLE_STREAM_BULK_SCAN</code></a> for that input.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: parsing from a <code>FILE*</code> (default)</summary> <p>The file is locked once while it is parsed:</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;cstdio&gt;</span>
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
@@ -23,4 +23,4 @@
 <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>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>f</span><span class=p>);</span><span class=w>  </span><span class=c1>// std::fgetc for every character</span>
 <span class=w>    </span><span class=n>std</span><span class=o>::</span><span class=n>fclose</span><span class=p>(</span><span class=n>f</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=../../basic_json/parse/ ><strong>parse</strong></a> - deserialize from a compatible input</li> <li><a href=../../basic_json/sax_parse/ ><strong>sax_parse</strong></a> - generate <abbr title="Simple API for XML">SAX</abbr> events</li> <li><a href=../json_disable_stream_bulk_scan/ ><strong>JSON_DISABLE_STREAM_BULK_SCAN</strong></a> - read a <code>std::istream</code> one character at a time</li> <li><a href=../../../features/parsing/#input-sources-and-performance>Parsing: input sources and performance</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 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</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 19, 2026 20:00:58 UTC">October 19, 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/parse/ ><strong>parse</strong></a> - deserialize from a compatible input</li> <li><a href=../../basic_json/sax_parse/ ><strong>sax_parse</strong></a> - generate <abbr title="Simple API for XML">SAX</abbr> events</li> <li><a href=../json_disable_stream_bulk_scan/ ><strong>JSON_DISABLE_STREAM_BULK_SCAN</strong></a> - read a <code>std::istream</code> one character at a time</li> <li><a href=../../../features/parsing/#input-sources-and-performance>Parsing: input sources and performance</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 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</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 21, 2026 08:22:50 UTC">October 21, 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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api/macros/json_disable_unlocked_file_io/index.md

@@ -8,6 +8,8 @@ When defined to `1`, parsing from a `FILE*` reads every character with `std::fge
 
 It does not change any result: values, exceptions, and the position of the file after parsing are the same either way. Only the speed and the locking of the file differ (see the notes on locking below).
 
+Builds with MemorySanitizer use `std::fgetc` automatically, because the inline `getc_unlocked` of glibc reads the stdio buffer directly, which glibc (not instrumented) filled, and MemorySanitizer would report it as uninitialized.
+
 ## Default definition
 
 The default value is `0`: the file is locked once and read with the unlocked stdio functions where they are available.

features/performance.md

@@ -20,32 +20,39 @@ below apply on every supported standard. This adapter exposes two optimizations
 
 - it can reconstruct already-consumed input on demand for error messages, instead of copying every character as it is
   read, and
-- the lexer can scan ordinary string characters directly out of the buffer, several bytes at a time, rather than one
-  character (and one function call) at a time.
+- the lexer can scan ordinary string characters, numbers, and indentation directly out of the buffer, several bytes at
+  a time, rather than one character (and one function call) at a time.
 
-A `#!cpp std::istream` (including `#!cpp std::ifstream`) or `#!cpp FILE*`, by contrast, is read through
-`input_stream_adapter` or `file_input_adapter`, which read one character (or one block, for binary formats) at a time
-and expose neither optimization -- the lexer falls back to the same byte-at-a-time path it uses for any
-non-contiguous, general-purpose iterator range. An iterator pair over non-contiguous but random-access storage (e.g.
-`#!cpp std::deque<char>::iterator`) gets the first optimization but not the second, since the byte-scanning fast path
-additionally requires contiguous storage.
+A `#!cpp std::istream` (including `#!cpp std::ifstream`) gets the same bulk scanning: `input_stream_adapter` scans the
+characters its stream buffer already holds (the *get area*) and asks the stream buffer for more only when they are used
+up. Nothing is read ahead, so the stream is left exactly where it would be after reading one character at a time, and
+[`operator>>`](../api/operator_gtgt.md) can still read several values from one stream. A stream buffer without a get
+area is read one character at a time. A `#!cpp FILE*` is still read one character at a time, but `file_input_adapter`
+locks the file once per parse instead of once per character. See
+[input sources and performance](parsing/index.md#input-sources-and-performance) for the full table. According to the
+description of [#5828](https://github.com/nlohmann/json/pull/5828), parsing from a stream is within about 10 to 20 % of
+parsing an equivalent `#!cpp std::string`.
 
-Practically: if the JSON text is already in memory, or small enough to read into memory, prefer passing a
-`#!cpp std::string`, a `#!cpp std::vector<char>`, or a pointer range to `parse` over a `#!cpp std::istream`. For a
-file, that means reading it into a string first and then parsing the string, rather than passing a
-`#!cpp std::ifstream` directly to `parse` -- the latter never benefits from either optimization:
+Inputs that are still read one character at a time: iterator ranges that are not contiguous (e.g.
+`#!cpp std::list<char>` or `#!cpp std::istreambuf_iterator<char>`), wide strings, and user-defined adapters. An
+iterator pair over non-contiguous but random-access storage (e.g. `#!cpp std::deque<char>::iterator`) gets the first
+optimization but not the second, since the byte-scanning fast path requires contiguous storage.
+
+Practically: a file can be passed directly to `parse`, which also avoids the memory for a copy of the file. Reading it
+into a string first is no longer necessary for speed:
 
 ```cpp
-// gets the contiguous fast paths
+// fast: the stream buffer's get area is scanned in bulk
 std::ifstream f("example.json");
-std::string contents((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
-json j = json::parse(contents);
-
-// does not: input_stream_adapter has no fast path
-std::ifstream f2("example.json");
-json j2 = json::parse(f2);
+json j = json::parse(f);
 ```
 
+Two macros switch the stream optimizations off without changing any result:
+[`JSON_DISABLE_STREAM_BULK_SCAN`](../api/macros/json_disable_stream_bulk_scan.md) for stream buffers that do not follow
+the usual `#!cpp std::streambuf` contract, and
+[`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md) for programs in which another thread
+must use the same `#!cpp FILE` object while it is parsed.
+
 For contiguous input with many non-ASCII characters, [`JSON_USE_SIMDUTF`](../api/macros/json_use_simdutf.md) can
 additionally speed up UTF-8 validation by using the [simdutf](https://github.com/simdutf/simdutf) library instead of
 the built-in scalar validator; streaming inputs (files, `#!cpp std::istream`, wide strings, user-defined adapters)

features/performance/index.html

@@ -1,12 +1,7 @@
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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/features/performance/" rel="canonical"><link href=../object_order/ rel=prev><link href=../parsing/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Performance - 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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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"/></svg> </label> <div class=md-searcLine truncated
 <span class=n>std</span><span class=o>::</span><span class=n>ifstream</span><span class=w> </span><span class=n>f</span><span class=p>(</span><span class=s>"example.json"</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=nf>contents</span><span class=p>((</span><span class=n>std</span><span class=o>::</span><span class=n>istreambuf_iterator</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=p>(</span><span class=n>f</span><span class=p>)),</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>istreambuf_iterator</span><span class=o>&lt;</span><span class=kt>char</span><span class=o>&gt;</span><span class=p>());</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>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>contents</span><span class=p>);</span>
-
-<span class=c1>// does not: input_stream_adapter has no fast path</span>
-<span class=n>std</span><span class=o>::</span><span class=n>ifstream</span><span class=w> </span><span class=n>f2</span><span class=p>(</span><span class=s>"example.json"</span><span class=p>);</span>
-<span class=n>json</span><span class=w> </span><span class=n>j2</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>f2</span><span class=p>);</span>
-</code></pre></div> <p>For contiguous input with many non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters, <a href=../../api/macros/json_use_simdutf/ ><code>JSON_USE_SIMDUTF</code></a> can additionally speed up <abbr title="Unicode Transformation Format">UTF</abbr>-8 validation by using the <a href="https://github.com/simdutf/simdutf">simdutf</a> library instead of the built-in scalar validator; streaming inputs (files, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code>, wide strings, user-defined adapters) always use the scalar path regardless of this macro.</p> <h2 id=large-documents>Large documents<a class=headerlink href=#large-documents title="Permanent link">&para;</a></h2> <p>Parsing always produces <abbr title="Simple API for XML">SAX</abbr> events internally; <a href=../../api/basic_json/parse/ ><code>parse</code></a> simply feeds them to a consumer that builds a complete <code>basic_json</code> value tree (a <abbr title="Document Object Model">DOM</abbr>) in memory. For documents too large to comfortably hold as a <abbr title="Document Object Model">DOM</abbr>, three alternatives avoid building it:</p> <ul> <li>Implement the <a href=../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> directly and pass it to <a href=../../api/basic_json/sax_parse/ ><code>sax_parse</code></a>; only the parts of the input you choose to keep ever become <code>basic_json</code> values.</li> <li>Pass a <a href=../parsing/parser_callbacks/ >parser callback</a> to <code>parse</code>. This still builds a <abbr title="Document Object Model">DOM</abbr>, but the callback can discard finished elements as soon as they are handled, so memory usage stays bounded by one element (plus the unparsed remainder of the input) instead of the whole document -- see the <a href=../parsing/parser_callbacks/#recipe-streaming-a-large-homogeneous-array>recipe for streaming a large homogeneous array</a>.</li> <li>Parse into a <a href=../json_view/ ><code>json_document</code></a> (<code class=highlight><span class=o>&lt;</span><span class=n>nlohmann</span><span class=o>/</span><span class=n>json_view</span><span class=p>.</span><span class=n>hpp</span><span class=o>&gt;</span></code>) instead of a <code>basic_json</code>. It keeps the input text and builds a flat index of 16 bytes per value; strings and floating-point numbers are not copied, but read from the text when needed. Read-only <a href=../../api/basic_json_view/ >views</a> give the familiar element access, and only the parts you <a href=../../api/basic_json_view/materialize/ ><code>materialize()</code></a> become <code>basic_json</code> values. A document that borrows the text instead of owning a copy needs the text to outlive it; see <a href=../json_view/#choosing-between-json-ordered_json-the-sax-interface-and-json_view>choosing between <code>json</code>, the <abbr title="Simple API for XML">SAX</abbr> interface, and <code>json_view</code></a>.</li> </ul> <p>If the data is naturally record-oriented, consider <a href=../parsing/json_lines/ ><abbr title="JavaScript Object Notation">JSON</abbr> Lines</a> instead of one large <abbr title="JavaScript Object Notation">JSON</abbr> document: reading and parsing it line by line with <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>getline</span></code> means only one line's value is ever in memory at a time, and a malformed line does not invalidate lines already processed.</p> <h2 id=binary-formats>Binary formats<a class=headerlink href=#binary-formats title="Permanent link">&para;</a></h2> <p><abbr title="JavaScript Object Notation">JSON</abbr> text is not a compact format. If the data is only exchanged between programs (not read by humans), the <a href=../binary_formats/ >binary formats</a> -- <abbr title="Binary JData">BJData</abbr>, <abbr title="Binary Object Notation 8">BON8</abbr>, <abbr title="Binary JSON">BSON</abbr>, <abbr title="Concise Binary Object Representation">CBOR</abbr>, MessagePack, and <abbr title="Universal Binary JSON">UBJSON</abbr> -- encode the same values more compactly, which reduces both the bytes transferred and, for most of them, the work needed to parse them back. The <a href=../binary_formats/#sizes>size comparison</a> on that page, measured against minified <abbr title="JavaScript Object Notation">JSON</abbr> for four reference documents, shows the effect varies a lot by document shape: <abbr title="Concise Binary Object Representation">CBOR</abbr> and MessagePack come out at 50.5% of the minified <abbr title="JavaScript Object Notation">JSON</abbr> size for the numeric-array-heavy <code>canada.json</code>, but only around 87-88% for the string-heavy <code>jeopardy.json</code>, where there is less numeric data to encode more compactly. <abbr title="Binary Object Notation 8">BON8</abbr> is the most compact option in that comparison for text-heavy documenLine truncated
+<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>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>f</span><span class=p>);</span>
+</code></pre></div> <p>Two macros switch the stream optimizations off without changing any result: <a href=../../api/macros/json_disable_stream_bulk_scan/ ><code>JSON_DISABLE_STREAM_BULK_SCAN</code></a> for stream buffers that do not follow the usual <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>streambuf</span></code> contract, and <a href=../../api/macros/json_disable_unlocked_file_io/ ><code>JSON_DISABLE_UNLOCKED_FILE_IO</code></a> for programs in which another thread must use the same <code class=highlight><span class=kt>FILE</span></code> object while it is parsed.</p> <p>For contiguous input with many non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters, <a href=../../api/macros/json_use_simdutf/ ><code>JSON_USE_SIMDUTF</code></a> can additionally speed up <abbr title="Unicode Transformation Format">UTF</abbr>-8 validation by using the <a href="https://github.com/simdutf/simdutf">simdutf</a> library instead of the built-in scalar validator; streaming inputs (files, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code>, wide strings, user-defined adapters) always use the scalar path regardless of this macro.</p> <h2 id=large-documents>Large documents<a class=headerlink href=#large-documents title="Permanent link">&para;</a></h2> <p>Parsing always produces <abbr title="Simple API for XML">SAX</abbr> events internally; <a href=../../api/basic_json/parse/ ><code>parse</code></a> simply feeds them to a consumer that builds a complete <code>basic_json</code> value tree (a <abbr title="Document Object Model">DOM</abbr>) in memory. For documents too large to comfortably hold as a <abbr title="Document Object Model">DOM</abbr>, three alternatives avoid building it:</p> <ul> <li>Implement the <a href=../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> directly and pass it to <a href=../../api/basic_json/sax_parse/ ><code>sax_parse</code></a>; only the parts of the input you choose to keep ever become <code>basic_json</code> values.</li> <li>Pass a <a href=../parsing/parser_callbacks/ >parser callback</a> to <code>parse</code>. This still builds a <abbr title="Document Object Model">DOM</abbr>, but the callback can discard finished elements as soon as they are handled, so memory usage stays bounded by one element (plus the unparsed remainder of the input) instead of the whole document -- see the <a href=../parsing/parser_callbacks/#recipe-streaming-a-large-homogeneous-array>recipe for streaming a large homogeneous array</a>.</li> <li>Parse into a <a href=../json_view/ ><code>json_document</code></a> (<code class=highlight><span class=o>&lt;</span><span class=n>nlohmann</span><span class=o>/</span><span class=n>json_view</span><span class=p>.</span><span class=n>hpp</span><span class=o>&gt;</span></code>) instead of a <code>basic_json</code>. It keeps the input text and builds a flat index of 16 bytes per value; strings and floating-point numbers are not copied, but read from the text when needed. Read-only <a href=../../api/basic_json_view/ >views</a> give the familiar element access, and only the parts you <a href=../../api/basic_json_view/materialize/ ><code>materialize()</code></a> become <code>basic_json</code> values. A document that borrows the text instead of owning a copy needs the text to outlive it; see <a href=../json_view/#choosing-between-json-ordered_json-the-sax-interface-and-json_view>choosing between <code>json</code>, the <abbr title="Simple API for XML">SAX</abbr> interface, and <code>json_view</code></a>.</li> </ul> <p>If the data is naturally record-oriented, consider <a href=../parsing/json_lines/ ><abbr title="JavaScript Object Notation">JSON</abbr> Lines</a> instead of one large <abbr title="JavaScript Object Notation">JSON</abbr> document: reading and parsing it line by line with <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>getline</span></code> means only one line's value is ever in memory at a time, and a malformed line does not invalidate lines already processed.</p> <h2 id=binary-formats>Binary formats<a class=headerlink href=#binary-formats title="Permanent link">&para;</a></h2> <p><abbr title="JavaScript Object Notation">JSON</abbr> text is not a compact format. If the data is only exchanged between programs (not read by humans), the <a href=../binary_formats/ >binary formats</a> -- <abbr title="Binary JData">BJData</abbr>, <abbr title="Binary Object Notation 8">BON8</abbr>, <abbr title="Binary JSON">BSON</abbr>, <abbr title="Concise Binary Object Representation">CBOR</abbr>, MessagePack, and <abbr title="Universal Binary JSON">UBJSON</abbr> -- encode the same values more compactly, which reduces both the bytes transferred and, for most of them, the work needed to parse them back. The <a href=../binary_formats/#sizes>size comparison</a> on that page, measured against minified <abbr titLine truncated
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_fwd.hpp&gt;</span>
 
 <span class=k>class</span><span class=w> </span><span class=nc>my_type</span>
@@ -19,4 +14,4 @@
 <span class=cp>#include</span><span class=w> </span><span class=cpf>"my_type.hpp"</span>
 
 <span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=nf>my_type::config</span><span class=p>()</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=p>{</span><span class=w> </span><span class=cm>/* ... */</span><span class=w> </span><span class=p>}</span>
-</code></pre></div> <p>One caveat: ABI-affecting macros such as <code>JSON_DIAGNOSTICS</code> and <code>JSON_DIAGNOSTIC_POSITIONS</code> are encoded into the library's <a href=../namespace/#limitations>inline namespace name</a>. Every translation unit -- whether it includes <code>json_fwd.hpp</code> or the full header -- must define them the same way, or linking fails with undefined references instead of a compile error.</p> <p>If I/O support is not needed at all, <a href=../../api/macros/json_no_io/ ><code>JSON_NO_IO</code></a> excludes <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> outright and drops the <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code>/<code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> <code>parse</code> overloads and <a href=../../api/operator_ltlt/ ><code>operator&lt;&lt;</code></a> that depend on them (<code>dump()</code> itself is unaffected, since it only returns a string); it exists for environments where those headers are unavailable (such as Intel SGX), and as a side effect those headers are then never processed by the compiler at all.</p> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../home/design_goals/ >Design goals</a> - why this library does not optimize for speed first</li> <li><a href=../../home/architecture/ >Architecture</a> - how input adapters, the lexer, and the serializer fit together</li> <li><a href=../parsing/ >Parsing</a> - the available parsing functions and inputs</li> <li><a href=../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> - parse without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../json_view/ >Zero-copy <abbr title="JavaScript Object Notation">JSON</abbr> views</a> - parse into a flat index of the text and read it without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../binary_formats/ >Binary formats</a> - compact alternatives to <abbr title="JavaScript Object Notation">JSON</abbr> text</li> <li><a href=../object_order/ >Object Order</a> - <code>json</code> vs. <code>ordered_json</code> and other <code>ObjectType</code> choices</li> <li><a href=../types/template_parameters/ >Template Parameter Requirements</a> - custom container and allocator types</li> <li><a href=../macros/ >Supported macros</a> - overview of all configuration macros, including the diagnostics ones above</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 21, 2026 08:21:27 UTC">October 21, 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-2Line truncated
+</code></pre></div> <p>One caveat: ABI-affecting macros such as <code>JSON_DIAGNOSTICS</code> and <code>JSON_DIAGNOSTIC_POSITIONS</code> are encoded into the library's <a href=../namespace/#limitations>inline namespace name</a>. Every translation unit -- whether it includes <code>json_fwd.hpp</code> or the full header -- must define them the same way, or linking fails with undefined references instead of a compile error.</p> <p>If I/O support is not needed at all, <a href=../../api/macros/json_no_io/ ><code>JSON_NO_IO</code></a> excludes <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> outright and drops the <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code>/<code class=highlight><span class=kt>FILE</span><span class=o>*</span></code> <code>parse</code> overloads and <a href=../../api/operator_ltlt/ ><code>operator&lt;&lt;</code></a> that depend on them (<code>dump()</code> itself is unaffected, since it only returns a string); it exists for environments where those headers are unavailable (such as Intel SGX), and as a side effect those headers are then never processed by the compiler at all.</p> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../home/design_goals/ >Design goals</a> - why this library does not optimize for speed first</li> <li><a href=../../home/architecture/ >Architecture</a> - how input adapters, the lexer, and the serializer fit together</li> <li><a href=../parsing/ >Parsing</a> - the available parsing functions and inputs</li> <li><a href=../parsing/sax_interface/ ><abbr title="Simple API for XML">SAX</abbr> interface</a> - parse without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../json_view/ >Zero-copy <abbr title="JavaScript Object Notation">JSON</abbr> views</a> - parse into a flat index of the text and read it without building a <abbr title="Document Object Model">DOM</abbr></li> <li><a href=../binary_formats/ >Binary formats</a> - compact alternatives to <abbr title="JavaScript Object Notation">JSON</abbr> text</li> <li><a href=../object_order/ >Object Order</a> - <code>json</code> vs. <code>ordered_json</code> and other <code>ObjectType</code> choices</li> <li><a href=../types/template_parameters/ >Template Parameter Requirements</a> - custom container and allocator types</li> <li><a href=../macros/ >Supported macros</a> - overview of all configuration macros, including the diagnostics ones above</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 21, 2026 10:25:10 UTC">October 21, 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-2Line truncated

features/performance/index.md

@@ -11,23 +11,22 @@ That said, how you use this library still makes a measurable difference. This pa
 For inputs backed by contiguous, single-byte memory -- a `std::string`, a `std::vector<char>`, a string literal, or a pointer range -- the library uses `iterator_input_adapter`, wrapped in a raw pointer so the fast paths below apply on every supported standard. This adapter exposes two optimizations the lexer detects at compile time:
 
 - it can reconstruct already-consumed input on demand for error messages, instead of copying every character as it is read, and
-- the lexer can scan ordinary string characters directly out of the buffer, several bytes at a time, rather than one character (and one function call) at a time.
+- the lexer can scan ordinary string characters, numbers, and indentation directly out of the buffer, several bytes at a time, rather than one character (and one function call) at a time.
 
-A `std::istream` (including `std::ifstream`) or `FILE*`, by contrast, is read through `input_stream_adapter` or `file_input_adapter`, which read one character (or one block, for binary formats) at a time and expose neither optimization -- the lexer falls back to the same byte-at-a-time path it uses for any non-contiguous, general-purpose iterator range. An iterator pair over non-contiguous but random-access storage (e.g. `std::deque<char>::iterator`) gets the first optimization but not the second, since the byte-scanning fast path additionally requires contiguous storage.
+A `std::istream` (including `std::ifstream`) gets the same bulk scanning: `input_stream_adapter` scans the characters its stream buffer already holds (the *get area*) and asks the stream buffer for more only when they are used up. Nothing is read ahead, so the stream is left exactly where it would be after reading one character at a time, and [`operator>>`](https://json.nlohmann.me/api/operator_gtgt/index.md) can still read several values from one stream. A stream buffer without a get area is read one character at a time. A `FILE*` is still read one character at a time, but `file_input_adapter` locks the file once per parse instead of once per character. See [input sources and performance](https://json.nlohmann.me/features/parsing/#input-sources-and-performance) for the full table. According to the description of [#5828](https://github.com/nlohmann/json/pull/5828), parsing from a stream is within about 10 to 20 % of parsing an equivalent `std::string`.
 
-Practically: if the JSON text is already in memory, or small enough to read into memory, prefer passing a `std::string`, a `std::vector<char>`, or a pointer range to `parse` over a `std::istream`. For a file, that means reading it into a string first and then parsing the string, rather than passing a `std::ifstream` directly to `parse` -- the latter never benefits from either optimization:
+Inputs that are still read one character at a time: iterator ranges that are not contiguous (e.g. `std::list<char>` or `std::istreambuf_iterator<char>`), wide strings, and user-defined adapters. An iterator pair over non-contiguous but random-access storage (e.g. `std::deque<char>::iterator`) gets the first optimization but not the second, since the byte-scanning fast path requires contiguous storage.
+
+Practically: a file can be passed directly to `parse`, which also avoids the memory for a copy of the file. Reading it into a string first is no longer necessary for speed:
 
 ```
-// gets the contiguous fast paths
+// fast: the stream buffer's get area is scanned in bulk
 std::ifstream f("example.json");
-std::string contents((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
-json j = json::parse(contents);
-
-// does not: input_stream_adapter has no fast path
-std::ifstream f2("example.json");
-json j2 = json::parse(f2);
+json j = json::parse(f);
 ```
 
+Two macros switch the stream optimizations off without changing any result: [`JSON_DISABLE_STREAM_BULK_SCAN`](https://json.nlohmann.me/api/macros/json_disable_stream_bulk_scan/index.md) for stream buffers that do not follow the usual `std::streambuf` contract, and [`JSON_DISABLE_UNLOCKED_FILE_IO`](https://json.nlohmann.me/api/macros/json_disable_unlocked_file_io/index.md) for programs in which another thread must use the same `FILE` object while it is parsed.
+
 For contiguous input with many non-ASCII characters, [`JSON_USE_SIMDUTF`](https://json.nlohmann.me/api/macros/json_use_simdutf/index.md) can additionally speed up UTF-8 validation by using the [simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator; streaming inputs (files, `std::istream`, wide strings, user-defined adapters) always use the scalar path regardless of this macro.
 
 ## Large documents

home/exceptions.md

@@ -1106,9 +1106,19 @@ double-precision number when `number_float_t` is `#!cpp float`.
 
 ### json.exception.out_of_range.407
 
-An unsigned integer number greater than 9223372036854775807 cannot be represented in the binary format. This exception
-is only thrown by [`to_bon8`](../api/basic_json/to_bon8.md), as [BON8](../features/binary_formats/bon8.md) has no
-unsigned 64-bit integer type.
+An integer number cannot be represented by the binary format it is serialized to:
+
+- [BON8](../features/binary_formats/bon8.md) only stores integers that fit into int64, so
+  [`to_bon8`](../api/basic_json/to_bon8.md) throws for unsigned integers greater than 9223372036854775807.
+- [CBOR](../features/binary_formats/cbor.md), [MessagePack](../features/binary_formats/messagepack.md), and
+  [BSON](../features/binary_formats/bson.md) store integers in at most 64 bits. With the default number types, every
+  integer fits, but a [`number_integer_t`](../api/basic_json/number_integer_t.md) or
+  [`number_unsigned_t`](../api/basic_json/number_unsigned_t.md) wider than 64 bits (e.g., `__int128`) can hold values
+  outside the range of the format: [-2^64, 2^64-1] for CBOR, [-2^63, 2^64-1] for MessagePack, and the range of int64
+  (signed integers) or uint64 (unsigned integers) for BSON.
+
+[UBJSON](../features/binary_formats/ubjson.md) and [BJData](../features/binary_formats/bjdata.md) never throw this
+exception, because they serialize integers beyond 64 bits as high-precision numbers.
 
 !!! note "Former occurrences"
 
@@ -1117,11 +1127,17 @@ unsigned 64-bit integer type.
     - Since version 3.9.0, integer numbers beyond int64 are serialized as high-precision UBJSON numbers.
     - Since version 3.12.0, integer numbers beyond int64 are serialized as uint64 BSON numbers.
 
-!!! failure "Example message"
+    Before version 3.13.0, CBOR, MessagePack, and BSON silently truncated integers wider than 64 bits, and BJData
+    truncated unsigned integers wider than 64 bits.
+
+!!! failure "Example messages"
 
     ```
     integer number 18446744073709551615 cannot be represented by BON8 as it does not fit int64
     ```
+    ```
+    integer number 1267650600228229401496703205376 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]
+    ```
 
 ### json.exception.out_of_range.408
 

home/exceptions/index.html

@@ -257,8 +257,9 @@ exception id: 401
 </code></pre></div> </div> <h3 id=jsonexceptionout_of_range405>json.exception.out_of_range.405<a class=headerlink href=#jsonexceptionout_of_range405 title="Permanent link">&para;</a></h3> <p>The <abbr title="JavaScript Object Notation">JSON</abbr> Patch operations 'remove' and 'move' cannot be applied to the root element of the <abbr title="JavaScript Object Notation">JSON</abbr> value. The exception is also thrown when the parent or a reference token of an empty <abbr title="JavaScript Object Notation">JSON</abbr> Pointer is requested, for instance by <a href=../../api/json_pointer/back/ ><code>back</code></a> or <a href=../../api/json_pointer/pop_back/ ><code>pop_back</code></a>.</p> <div class="admonition failure"> <p class=admonition-title>Example message</p> <div class=highlight><pre><span></span><code>JSON pointer has no parent
 </code></pre></div> </div> <h3 id=jsonexceptionout_of_range406>json.exception.out_of_range.406<a class=headerlink href=#jsonexceptionout_of_range406 title="Permanent link">&para;</a></h3> <p>A parsed number could not be stored without changing it to <abbr title="Not a Number">NaN</abbr> or INF. For the binary formats, this happens when a finite floating-point number does not fit into <a href=../../api/basic_json/number_float_t/ ><code>number_float_t</code></a>, for example a double-precision number when <code>number_float_t</code> is <code class=highlight><span class=kt>float</span></code>.</p> <div class="admonition failure"> <p class=admonition-title>Example messages</p> <p><div class=highlight><pre><span></span><code>number overflow parsing '10E1000'
 </code></pre></div> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.406] syntax error while parsing CBOR value: number overflow
-</code></pre></div></p> </div> <h3 id=jsonexceptionout_of_range407>json.exception.out_of_range.407<a class=headerlink href=#jsonexceptionout_of_range407 title="Permanent link">&para;</a></h3> <p>An unsigned integer number greater than 9223372036854775807 cannot be represented in the binary format. This exception is only thrown by <a href=../../api/basic_json/to_bon8/ ><code>to_bon8</code></a>, as <a href=../../features/binary_formats/bon8/ ><abbr title="Binary Object Notation 8">BON8</abbr></a> has no unsigned 64-bit integer type.</p> <div class="admonition note"> <p class=admonition-title>Former occurrences</p> <p>The <abbr title="Universal Binary JSON">UBJSON</abbr> and <abbr title="Binary JSON">BSON</abbr> writers used to throw this exception as well:</p> <ul> <li>Since version 3.9.0, integer numbers beyond int64 are serialized as high-precision <abbr title="Universal Binary JSON">UBJSON</abbr> numbers.</li> <li>Since version 3.12.0, integer numbers beyond int64 are serialized as uint64 <abbr title="Binary JSON">BSON</abbr> numbers.</li> </ul> </div> <div class="admonition failure"> <p class=admonition-title>Example message</p> <div class=highlight><pre><span></span><code>integer number 18446744073709551615 cannot be represented by BON8 as it does not fit int64
-</code></pre></div> </div> <h3 id=jsonexceptionout_of_range408>json.exception.out_of_range.408<a class=headerlink href=#jsonexceptionout_of_range408 title="Permanent link">&para;</a></h3> <p>The size of an array or object in a <a href=../../features/binary_formats/ >binary format</a> exceeds the maximal capacity: the size following <code>#</code> for <a href=../../features/binary_formats/ubjson/ ><abbr title="Universal Binary JSON">UBJSON</abbr></a>/<a href=../../features/binary_formats/bjdata/ ><abbr title="Binary JData">BJData</abbr></a>, or the encoded length for <a href=../../features/binary_formats/cbor/ ><abbr title="Concise Binary Object Representation">CBOR</abbr></a>.</p> <p>The exception is also thrown for a <a href=../../features/binary_formats/ubjson/ ><abbr title="Universal Binary JSON">UBJSON</abbr></a> array of a type that is encoded by its marker alone (<code>Z</code>, <code>T</code> or <code>F</code>) whose declared count exceeds 1,048,576 (<code>1 &lt;&lt; 20</code>). Such an array has no payload, so its count alone decides how much memory is allocated, and a handful of bytes would otherwise describe billions of values. <a href=../../api/basic_json/to_ubjson/ ><code>to_ubjson</code></a> writes longer arrays of these types without the size and type annotation, so any value it produces can still be read back.</p> <div class="admonition failure"> <p class=admonition-title>Example messages</p> <p><div class=highlight><pre><span></span><code>excessive array size: 8658170730974374167
+</code></pre></div></p> </div> <h3 id=jsonexceptionout_of_range407>json.exception.out_of_range.407<a class=headerlink href=#jsonexceptionout_of_range407 title="Permanent link">&para;</a></h3> <p>An integer number cannot be represented by the binary format it is serialized to:</p> <ul> <li><a href=../../features/binary_formats/bon8/ ><abbr title="Binary Object Notation 8">BON8</abbr></a> only stores integers that fit into int64, so <a href=../../api/basic_json/to_bon8/ ><code>to_bon8</code></a> throws for unsigned integers greater than 9223372036854775807.</li> <li><a href=../../features/binary_formats/cbor/ ><abbr title="Concise Binary Object Representation">CBOR</abbr></a>, <a href=../../features/binary_formats/messagepack/ >MessagePack</a>, and <a href=../../features/binary_formats/bson/ ><abbr title="Binary JSON">BSON</abbr></a> store integers in at most 64 bits. With the default number types, every integer fits, but a <a href=../../api/basic_json/number_integer_t/ ><code>number_integer_t</code></a> or <a href=../../api/basic_json/number_unsigned_t/ ><code>number_unsigned_t</code></a> wider than 64 bits (e.g., <code>__int128</code>) can hold values outside the range of the format: [-2^64, 2^64-1] for <abbr title="Concise Binary Object Representation">CBOR</abbr>, [-2^63, 2^64-1] for MessagePack, and the range of int64 (signed integers) or uint64 (unsigned integers) for <abbr title="Binary JSON">BSON</abbr>.</li> </ul> <p><a href=../../features/binary_formats/ubjson/ ><abbr title="Universal Binary JSON">UBJSON</abbr></a> and <a href=../../features/binary_formats/bjdata/ ><abbr title="Binary JData">BJData</abbr></a> never throw this exception, because they serialize integers beyond 64 bits as high-precision numbers.</p> <div class="admonition note"> <p class=admonition-title>Former occurrences</p> <p>The <abbr title="Universal Binary JSON">UBJSON</abbr> and <abbr title="Binary JSON">BSON</abbr> writers used to throw this exception as well:</p> <ul> <li>Since version 3.9.0, integer numbers beyond int64 are serialized as high-precision <abbr title="Universal Binary JSON">UBJSON</abbr> numbers.</li> <li>Since version 3.12.0, integer numbers beyond int64 are serialized as uint64 <abbr title="Binary JSON">BSON</abbr> numbers.</li> </ul> <p>Before version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>, <abbr title="Concise Binary Object Representation">CBOR</abbr>, MessagePack, and <abbr title="Binary JSON">BSON</abbr> silently truncated integers wider than 64 bits, and <abbr title="Binary JData">BJData</abbr> truncated unsigned integers wider than 64 bits.</p> </div> <div class="admonition failure"> <p class=admonition-title>Example messages</p> <p><div class=highlight><pre><span></span><code>integer number 18446744073709551615 cannot be represented by BON8 as it does not fit int64
+</code></pre></div> <div class=highlight><pre><span></span><code>integer number 1267650600228229401496703205376 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]
+</code></pre></div></p> </div> <h3 id=jsonexceptionout_of_range408>json.exception.out_of_range.408<a class=headerlink href=#jsonexceptionout_of_range408 title="Permanent link">&para;</a></h3> <p>The size of an array or object in a <a href=../../features/binary_formats/ >binary format</a> exceeds the maximal capacity: the size following <code>#</code> for <a href=../../features/binary_formats/ubjson/ ><abbr title="Universal Binary JSON">UBJSON</abbr></a>/<a href=../../features/binary_formats/bjdata/ ><abbr title="Binary JData">BJData</abbr></a>, or the encoded length for <a href=../../features/binary_formats/cbor/ ><abbr title="Concise Binary Object Representation">CBOR</abbr></a>.</p> <p>The exception is also thrown for a <a href=../../features/binary_formats/ubjson/ ><abbr title="Universal Binary JSON">UBJSON</abbr></a> array of a type that is encoded by its marker alone (<code>Z</code>, <code>T</code> or <code>F</code>) whose declared count exceeds 1,048,576 (<code>1 &lt;&lt; 20</code>). Such an array has no payload, so its count alone decides how much memory is allocated, and a handful of bytes would otherwise describe billions of values. <a href=../../api/basic_json/to_ubjson/ ><code>to_ubjson</code></a> writes longer arrays of these types without the size and type annotation, so any value it produces can still be read back.</p> <div class="admonition failure"> <p class=admonition-title>Example messages</p> <p><div class=highlight><pre><span></span><code>excessive array size: 8658170730974374167
 </code></pre></div> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.408] syntax error while parsing CBOR size: excessive array size
 </code></pre></div> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.408] syntax error while parsing CBOR size: excessive map size
 </code></pre></div> <div class=highlight><pre><span></span><code>[json.exception.out_of_range.408] syntax error while parsing UBJSON size: excessive array size
@@ -308,4 +309,4 @@ array index 18446744073709551616 exceeds size_type
 exception id: 501
 </code></pre></div> </details> <h3 id=jsonexceptionother_error501>json.exception.other_error.501<a class=headerlink href=#jsonexceptionother_error501 title="Permanent link">&para;</a></h3> <p>A <abbr title="JavaScript Object Notation">JSON</abbr> Patch operation 'test' failed. The unsuccessful operation is also printed.</p> <div class="admonition failure"> <p class=admonition-title>Example message</p> <p>Executing <code class=highlight><span class=p>{</span><span class=nt>"op"</span><span class=p>:</span><span class=s2>"test"</span><span class=p>,</span><span class=w> </span><span class=nt>"path"</span><span class=p>:</span><span class=s2>"/baz"</span><span class=p>,</span><span class=w> </span><span class=nt>"value"</span><span class=p>:</span><span class=s2>"bar"</span><span class=p>}</span></code> on <code class=highlight><span class=p>{</span><span class=nt>"baz"</span><span class=p>:</span><span class=w> </span><span class=s2>"qux"</span><span class=p>}</span></code>:</p> <div class=highlight><pre><span></span><code>[json.exception.other_error.501] unsuccessful: {"op":"test","path":"/baz","value":"bar"}
 </code></pre></div> </div> <h3 id=jsonexceptionother_error502>json.exception.other_error.502<a class=headerlink href=#jsonexceptionother_error502 title="Permanent link">&para;</a></h3> <p><a href=../../api/basic_json/to_ubjson/ ><code>to_ubjson</code></a> and <a href=../../api/basic_json/to_bjdata/ ><code>to_bjdata</code></a> were called with <code>use_type = true</code> but <code>use_size = false</code>. <abbr title="Universal Binary JSON">UBJSON</abbr> requires a size marker (<code>#</code>) after a type marker (<code>$</code>).</p> <div class="admonition failure"> <p class=admonition-title>Example message</p> <div class=highlight><pre><span></span><code>[json.exception.other_error.502] use_type requires use_size = true
-</code></pre></div> </div> <div class="admonition note"> <p class=admonition-title>Note</p> <p>This exception was added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Before that, debug builds aborted on an assertion and release builds wrote a <code>$</code> marker without <code>#</code>, which <a href=../../api/basic_json/from_ubjson/ ><code>from_ubjson</code></a> then rejected.</p> </div> <!-- 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 21, 2026 08:21:29 UTC">October 21, 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=http://www.w3.org/2000/svg viewbox="0 0 384 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.Line truncated
+</code></pre></div> </div> <div class="admonition note"> <p class=admonition-title>Note</p> <p>This exception was added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Before that, debug builds aborted on an assertion and release builds wrote a <code>$</code> marker without <code>#</code>, which <a href=../../api/basic_json/from_ubjson/ ><code>from_ubjson</code></a> then rejected.</p> </div> <!-- 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 21, 2026 08:36:31 UTC">October 21, 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=http://www.w3.org/2000/svg viewbox="0 0 384 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.Line truncated

home/exceptions/index.md

@@ -1078,7 +1078,12 @@ number overflow parsing '10E1000'
 
 ### json.exception.out_of_range.407
 
-An unsigned integer number greater than 9223372036854775807 cannot be represented in the binary format. This exception is only thrown by [`to_bon8`](https://json.nlohmann.me/api/basic_json/to_bon8/index.md), as [BON8](https://json.nlohmann.me/features/binary_formats/bon8/index.md) has no unsigned 64-bit integer type.
+An integer number cannot be represented by the binary format it is serialized to:
+
+- [BON8](https://json.nlohmann.me/features/binary_formats/bon8/index.md) only stores integers that fit into int64, so [`to_bon8`](https://json.nlohmann.me/api/basic_json/to_bon8/index.md) throws for unsigned integers greater than 9223372036854775807.
+- [CBOR](https://json.nlohmann.me/features/binary_formats/cbor/index.md), [MessagePack](https://json.nlohmann.me/features/binary_formats/messagepack/index.md), and [BSON](https://json.nlohmann.me/features/binary_formats/bson/index.md) store integers in at most 64 bits. With the default number types, every integer fits, but a [`number_integer_t`](https://json.nlohmann.me/api/basic_json/number_integer_t/index.md) or [`number_unsigned_t`](https://json.nlohmann.me/api/basic_json/number_unsigned_t/index.md) wider than 64 bits (e.g., `__int128`) can hold values outside the range of the format: [-2^64, 2^64-1] for CBOR, [-2^63, 2^64-1] for MessagePack, and the range of int64 (signed integers) or uint64 (unsigned integers) for BSON.
+
+[UBJSON](https://json.nlohmann.me/features/binary_formats/ubjson/index.md) and [BJData](https://json.nlohmann.me/features/binary_formats/bjdata/index.md) never throw this exception, because they serialize integers beyond 64 bits as high-precision numbers.
 
 Former occurrences
 
@@ -1087,12 +1092,18 @@ The UBJSON and BSON writers used to throw this exception as well:
 - Since version 3.9.0, integer numbers beyond int64 are serialized as high-precision UBJSON numbers.
 - Since version 3.12.0, integer numbers beyond int64 are serialized as uint64 BSON numbers.
 
-Example message
+Before version 3.13.0 unreleased, CBOR, MessagePack, and BSON silently truncated integers wider than 64 bits, and BJData truncated unsigned integers wider than 64 bits.
+
+Example messages
 
 ```
 integer number 18446744073709551615 cannot be represented by BON8 as it does not fit int64
 ```
 
+```
+integer number 1267650600228229401496703205376 cannot be represented by CBOR as it does not fit [-2^64, 2^64-1]
+```
+
 ### json.exception.out_of_range.408
 
 The size of an array or object in a [binary format](https://json.nlohmann.me/features/binary_formats/index.md) exceeds the maximal capacity: the size following `#` for [UBJSON](https://json.nlohmann.me/features/binary_formats/ubjson/index.md)/[BJData](https://json.nlohmann.me/features/binary_formats/bjdata/index.md), or the encoded length for [CBOR](https://json.nlohmann.me/features/binary_formats/cbor/index.md).

search/search_index.json

@@ -1 +1 @@
-{"config":{"lang":["en"],"separator":"[\\s\\-\\.]","pipeline":["stopWordFilter"],"fields":{"title":{"boost":1000.0},"text":{"boost":1.0},"tags":{"boost":1000000.0}}},"docs":[{"location":"","title":"JSON for Modern C++","text":"<p>JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-class C++ data type, using the operator magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like Python. The whole library is available as a single header, <code>json.hpp</code>, with no dependencies, no subproject, and no complex build system to set up; a companion header, <code>json_fwd.hpp</code>, provides forward declarations to keep compile times down. See header-only integration for details. It is heavily unit-tested with 100% code coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google OSS-Fuzz.</p>"},{"location":"#quick-start","title":"Quick start","text":"<p>Add the single header to your project and use the library like this:</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // parse a JSON string\n    json j = json::parse(R\"({\"happy\": true, \"pi\": 3.141})\");\n\n    // access and modify values\n    j[\"name\"] = \"Niels\";\n    j[\"list\"] = {1, 0, 2};\n\n    // serialize with an indent of 4 spaces\n    std::cout &lt;&lt; j.dump(4) &lt;&lt; '\\n';\n}\n</code></pre> <p>Get the library by copying the single header <code>json.hpp</code> from the releases page into a directory <code>nlohmann</code> on your include path, or by installing it with a package manager:</p> <pre><code>brew install nlohmann-json    # Homebrew\nvcpkg install nlohmann-json   # vcpkg\n</code></pre> <pre><code>find_package(nlohmann_json 3.12.0 REQUIRED)\ntarget_link_libraries(myproject PRIVATE nlohmann_json::nlohmann_json)\n</code></pre> <p>See Integration for CMake in detail, all supported package managers (Conan, Meson, Bazel, Conda, and more), and pkg-config.</p>"},{"location":"#explore-the-documentation","title":"Explore the documentation","text":"<ul> <li> <p> Features</p> <p>Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, and more.</p> <p> Features</p> </li> <li> <p> Integration</p> <p>Add the library to your project via a single header, CMake, a package manager, or pkg-config.</p> <p> Integration</p> </li> <li> <p> API documentation</p> <p>The complete reference for <code>basic_json</code> and its member functions, types, and related classes.</p> <p> API documentation</p> </li> <li> <p> FAQ</p> <p>Answers to common questions and known surprises when using the library.</p> <p> FAQ</p> </li> <li> <p> Releases</p> <p>What changed in each release, with links to the relevant documentation.</p> <p> Releases</p> </li> <li> <p> Community</p> <p>The ecosystem, contribution guidelines, governance, and quality assurance around the project.</p> <p> Community</p> </li> </ul> <p>Unreleased changes</p> <p>This documentation is built from the <code>develop</code> branch and may describe changes that are not part of a release yet. Their version numbers are followed by an unreleased badge; see Releases for what shipped in each version.</p> <p>The library is licensed under the MIT License. The source code, issue tracker, and discussions are on GitHub.</p>"},{"location":"api/json/","title":"nlohmann::json","text":"<pre><code>using json = basic_json&lt;&gt;;\n</code></pre> <p>This type is the default specialization of the basic_json class which uses the standard template types.</p>"},{"location":"api/json/#examples","title":"Examples","text":"Example <p>The example below demonstrates how to use the type <code>nlohmann::json</code>.</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;iomanip&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j =\n    {\n        {\"pi\", 3.141},\n        {\"happy\", true},\n        {\"name\", \"Niels\"},\n        {\"nothing\", nullptr},\n        {\n            \"answer\", {\n                {\"everything\", 42}\n            }\n        },\n        {\"list\", {1, 0, 2}},\n        {\n            \"object\", {\n                {\"currency\", \"USD\"},\n                {\"value\", 42.99}\n            }\n        }\n    };\n\n    // add new values\n    j[\"new\"][\"key\"][\"value\"] = {\"another\", \"list\"};\n\n    // count elements\n    auto s = j.size();\n    j[\"size\"] = s;\n\n    // pretty print with indent of 4 spaces\n    std::cout &lt;&lt; std::setw(4) &lt;&lt; j &lt;&lt; '\\n';\n}\n</code></pre> <p>Output:</p> <pre><code>{\n    \"answer\": {\n        \"everything\": 42\n    },\n    \"happy\": true,\n    \"list\": [\n        1,\n        0,\n        2\n    ],\n    \"name\": \"Niels\",\n    \"new\": {\n        \"key\": {\n            \"value\": [\n                \"another\",\n    Line truncated
+{"config":{"lang":["en"],"separator":"[\\s\\-\\.]","pipeline":["stopWordFilter"],"fields":{"title":{"boost":1000.0},"text":{"boost":1.0},"tags":{"boost":1000000.0}}},"docs":[{"location":"","title":"JSON for Modern C++","text":"<p>JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-class C++ data type, using the operator magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like Python. The whole library is available as a single header, <code>json.hpp</code>, with no dependencies, no subproject, and no complex build system to set up; a companion header, <code>json_fwd.hpp</code>, provides forward declarations to keep compile times down. See header-only integration for details. It is heavily unit-tested with 100% code coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google OSS-Fuzz.</p>"},{"location":"#quick-start","title":"Quick start","text":"<p>Add the single header to your project and use the library like this:</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // parse a JSON string\n    json j = json::parse(R\"({\"happy\": true, \"pi\": 3.141})\");\n\n    // access and modify values\n    j[\"name\"] = \"Niels\";\n    j[\"list\"] = {1, 0, 2};\n\n    // serialize with an indent of 4 spaces\n    std::cout &lt;&lt; j.dump(4) &lt;&lt; '\\n';\n}\n</code></pre> <p>Get the library by copying the single header <code>json.hpp</code> from the releases page into a directory <code>nlohmann</code> on your include path, or by installing it with a package manager:</p> <pre><code>brew install nlohmann-json    # Homebrew\nvcpkg install nlohmann-json   # vcpkg\n</code></pre> <pre><code>find_package(nlohmann_json 3.12.0 REQUIRED)\ntarget_link_libraries(myproject PRIVATE nlohmann_json::nlohmann_json)\n</code></pre> <p>See Integration for CMake in detail, all supported package managers (Conan, Meson, Bazel, Conda, and more), and pkg-config.</p>"},{"location":"#explore-the-documentation","title":"Explore the documentation","text":"<ul> <li> <p> Features</p> <p>Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, and more.</p> <p> Features</p> </li> <li> <p> Integration</p> <p>Add the library to your project via a single header, CMake, a package manager, or pkg-config.</p> <p> Integration</p> </li> <li> <p> API documentation</p> <p>The complete reference for <code>basic_json</code> and its member functions, types, and related classes.</p> <p> API documentation</p> </li> <li> <p> FAQ</p> <p>Answers to common questions and known surprises when using the library.</p> <p> FAQ</p> </li> <li> <p> Releases</p> <p>What changed in each release, with links to the relevant documentation.</p> <p> Releases</p> </li> <li> <p> Community</p> <p>The ecosystem, contribution guidelines, governance, and quality assurance around the project.</p> <p> Community</p> </li> </ul> <p>Unreleased changes</p> <p>This documentation is built from the <code>develop</code> branch and may describe changes that are not part of a release yet. Their version numbers are followed by an unreleased badge; see Releases for what shipped in each version.</p> <p>The library is licensed under the MIT License. The source code, issue tracker, and discussions are on GitHub.</p>"},{"location":"api/json/","title":"nlohmann::json","text":"<pre><code>using json = basic_json&lt;&gt;;\n</code></pre> <p>This type is the default specialization of the basic_json class which uses the standard template types.</p>"},{"location":"api/json/#examples","title":"Examples","text":"Example <p>The example below demonstrates how to use the type <code>nlohmann::json</code>.</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;iomanip&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing json = nlohmann::json;\n\nint main()\n{\n    // create a JSON object\n    json j =\n    {\n        {\"pi\", 3.141},\n        {\"happy\", true},\n        {\"name\", \"Niels\"},\n        {\"nothing\", nullptr},\n        {\n            \"answer\", {\n                {\"everything\", 42}\n            }\n        },\n        {\"list\", {1, 0, 2}},\n        {\n            \"object\", {\n                {\"currency\", \"USD\"},\n                {\"value\", 42.99}\n            }\n        }\n    };\n\n    // add new values\n    j[\"new\"][\"key\"][\"value\"] = {\"another\", \"list\"};\n\n    // count elements\n    auto s = j.size();\n    j[\"size\"] = s;\n\n    // pretty print with indent of 4 spaces\n    std::cout &lt;&lt; std::setw(4) &lt;&lt; j &lt;&lt; '\\n';\n}\n</code></pre> <p>Output:</p> <pre><code>{\n    \"answer\": {\n        \"everything\": 42\n    },\n    \"happy\": true,\n    \"list\": [\n        1,\n        0,\n        2\n    ],\n    \"name\": \"Niels\",\n    \"new\": {\n        \"key\": {\n            \"value\": [\n                \"another\",\n    Line truncated