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href="https://pub.dev" target="_blank" rel="noopener">Package site</a></li></ul></li></ul></div></div><main id="page-content"><div id="site-toc--side" class="site-toc"><header class="site-toc__title">Contents</header><ul class="section-nav"><li class="toc-entry nav-item"><a class="nav-link" href="#decoding-and-encoding-json">Decoding and encoding JSON</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#decoding-and-encoding-utf-8-characters">Decoding and encoding UTF-8 characters</a></li><li class="toc-entry nav-item"><a class="nav-link" href="#other-functionality">Other functionality</a></li></ul></div><article><div class="content"><nav id="subnav"><ul><li class="previous"><a href="/libraries/dart-math">⟨ dart:math</a></li><li class="next"><a href="/libraries/dart-io">dart:io ⟩</a></li></ul></nav><div id="site-content-title"><h1>dart:convert</h1></div><div id="site-toc--inline" class="site-toc"><header class="site-toc__title">Contents</header><ul class="section-nav"><li class="toc-entry"><a href="#decoding-and-encoding-json">Decoding and encoding JSON</a></li><li class="toc-entry"><a href="#decoding-and-encoding-utf-8-characters">Decoding and encoding UTF-8 characters</a></li><li class="toc-entry"><a href="#other-functionality">Other functionality</a></li></ul></div> <?code-excerpt replace="/ *\/\/\s+ignore_for_file:[^\n]+\n//g; /(^|\n) *\/\/\s+ignore:[^\n]+\n/$1/g; /(\n[^\n]+) *\/\/\s+ignore:[^\n]+\n/$1\n/g"?> <?code-excerpt plaster="none"?> <p>The dart:convert library (<a href="https://api.dart.dev/dart-convert/dart-convert-library.html">API reference</a>) has converters for JSON and UTF-8, as well as support for creating additional converters. <a href="https://www.json.org/">JSON</a> is a simple text format for representing structured objects and collections. <a href="https://en.wikipedia.org/wiki/UTF-8">UTF-8</a> is a common variable-width encoding that can represent every character in the Unicode character set.</p><p>To use this library, import dart:convert.</p> <?code-excerpt "misc/test/library_tour/convert_test.dart (import)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">import</span><span style="color:#11796D"> 'dart:convert'</span><span style="color:#222222">;</span></span></code></pre></div></div><div class="header-wrapper"><h2 id="decoding-and-encoding-json">Decoding and encoding JSON</h2><a class="heading-link" href="#decoding-and-encoding-json" aria-label="Link to 'Decoding and encoding JSON' section">#</a></div><p>Decode a JSON-encoded string into a Dart object with <code>jsonDecode()</code>:</p> <?code-excerpt "misc/test/library_tour/convert_test.dart (json-decode)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#6E6E70">// NOTE: Be sure to use double quotes ("),</span></span> <span class="line"><span style="color:#6E6E70">// not single quotes ('), inside the JSON string.</span></span> <span class="line"><span style="color:#6E6E70">// This string is JSON, not Dart.</span></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> jsonString = </span><span style="color:#11796D">'''</span></span> <span class="line"><span style="color:#11796D"> [</span></span> <span class="line"><span style="color:#11796D"> {"score": 40},</span></span> <span class="line"><span style="color:#11796D"> {"score": 80}</span></span> <span class="line"><span style="color:#11796D"> ]</span></span> <span class="line"><span style="color:#11796D">'''</span><span style="color:#222222">;</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> scores = </span><span style="color:#6200EE">jsonDecode</span><span style="color:#222222">(jsonString);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(scores is </span><span style="color:#0468D7">List</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> firstScore = scores[</span><span style="color:#11796D">0</span><span style="color:#222222">];</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(firstScore is </span><span style="color:#0468D7">Map</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(firstScore[</span><span style="color:#11796D">'score'</span><span style="color:#222222">] == </span><span style="color:#11796D">40</span><span style="color:#222222">);</span></span></code></pre></div></div><p>Encode a supported Dart object into a JSON-formatted string with <code>jsonEncode()</code>:</p> <?code-excerpt "misc/test/library_tour/convert_test.dart (json-encode)"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> scores = [</span></span> <span class="line"><span style="color:#222222"> {</span><span style="color:#11796D">'score'</span><span style="color:#222222">: </span><span style="color:#11796D">40</span><span style="color:#222222">},</span></span> <span class="line"><span style="color:#222222"> {</span><span style="color:#11796D">'score'</span><span style="color:#222222">: </span><span style="color:#11796D">80</span><span style="color:#222222">},</span></span> <span class="line"><span style="color:#222222"> {</span><span style="color:#11796D">'score'</span><span style="color:#222222">: </span><span style="color:#11796D">100</span><span style="color:#222222">, </span><span style="color:#11796D">'overtime'</span><span style="color:#222222">: </span><span style="color:#11796D">true</span><span style="color:#222222">, </span><span style="color:#11796D">'special_guest'</span><span style="color:#222222">: </span><span style="color:#11796D">null</span><span style="color:#222222">}</span></span> <span class="line"><span style="color:#222222">];</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> jsonText = </span><span style="color:#6200EE">jsonEncode</span><span style="color:#222222">(scores);</span></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(jsonText ==</span></span> <span class="line"><span style="color:#11796D"> '[{"score":40},{"score":80},'</span></span> <span class="line"><span style="color:#11796D"> '{"score":100,"overtime":true,'</span></span> <span class="line"><span style="color:#11796D"> '"special_guest":null}]'</span><span style="color:#222222">);</span></span></code></pre></div></div><p>Only objects of type int, double, String, bool, null, List, or Map (with string keys) are directly encodable into JSON. List and Map objects are encoded recursively.</p><p>You have two options for encoding objects that aren't directly encodable. The first is to invoke <code>jsonEncode()</code> with a second argument: a function that returns an object that is directly encodable. Your second option is to omit the second argument, in which case the encoder calls the object's <code>toJson()</code> method.</p><p>For more examples and links to JSON-related packages, see <a href="/guides/json">Using JSON</a>.</p><div class="header-wrapper"><h2 id="decoding-and-encoding-utf-8-characters">Decoding and encoding UTF-8 characters</h2><a class="heading-link" href="#decoding-and-encoding-utf-8-characters" aria-label="Link to 'Decoding and encoding UTF-8 characters' section">#</a></div><p>Use <code>utf8.decode()</code> to decode UTF8-encoded bytes to a Dart string:</p> <?code-excerpt "misc/test/library_tour/convert_test.dart (utf8-decode)" replace="/ \/\/line-br.*//g"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#0468D7">List</span><span style="color:#222222"><</span><span style="color:#0468D7">int</span><span style="color:#222222">> utf8Bytes = [</span></span> <span class="line"><span style="color:#11796D"> 0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0x8e</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xb1</span><span style="color:#222222">, </span><span style="color:#11796D">0xc5</span><span style="color:#222222">, </span><span style="color:#11796D">0xa3</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xa9</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#11796D"> 0x72</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xb1</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xa5</span><span style="color:#222222">, </span><span style="color:#11796D">0xc5</span><span style="color:#222222">, </span><span style="color:#11796D">0xa3</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#11796D"> 0xae</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xb6</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xb1</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xa5</span><span style="color:#222222">, </span><span style="color:#11796D">0xc4</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#11796D"> 0xbc</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xae</span><span style="color:#222222">, </span><span style="color:#11796D">0xc5</span><span style="color:#222222">, </span><span style="color:#11796D">0xbe</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xa5</span><span style="color:#222222">, </span><span style="color:#11796D">0xc5</span><span style="color:#222222">,</span></span> <span class="line"><span style="color:#11796D"> 0xa3</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xae</span><span style="color:#222222">, </span><span style="color:#11796D">0xe1</span><span style="color:#222222">, </span><span style="color:#11796D">0xbb</span><span style="color:#222222">, </span><span style="color:#11796D">0x9d</span><span style="color:#222222">, </span><span style="color:#11796D">0xc3</span><span style="color:#222222">, </span><span style="color:#11796D">0xb1</span></span> <span class="line"><span style="color:#222222">];</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> funnyWord = utf8.</span><span style="color:#6200EE">decode</span><span style="color:#222222">(utf8Bytes);</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(funnyWord == </span><span style="color:#11796D">'Îñţérñåţîöñåļîžåţîờñ'</span><span style="color:#222222">);</span></span></code></pre></div></div><p>To convert a stream of UTF-8 characters into a Dart string, specify <code>utf8.decoder</code> to the Stream <code>transform()</code> method:</p> <?code-excerpt "misc/test/library_tour/io_test.dart (utf8-decoder)" replace="/utf8.decoder/[!$&!]/g"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#D43324">var</span><span style="color:#222222"> lines = </span><mark class="highlight"><span style="color:#222222">utf8.decoder</span></mark><span style="color:#222222">.</span><span style="color:#6200EE">bind</span><span style="color:#222222">(inputStream).</span><span style="color:#6200EE">transform</span><span style="color:#222222">(</span><span style="color:#D43324">const</span><span style="color:#0468D7"> LineSplitter</span><span style="color:#222222">());</span></span> <span class="line"><span style="color:#D43324">try</span><span style="color:#222222"> {</span></span> <span class="line"><span style="color:#D43324"> await</span><span style="color:#D43324"> for</span><span style="color:#222222"> (</span><span style="color:#D43324">final</span><span style="color:#222222"> line </span><span style="color:#D43324">in</span><span style="color:#222222"> lines) {</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(</span><span style="color:#11796D">'Got </span><span style="color:#11796D">${</span><span style="color:#222222">line</span><span style="color:#11796D">.</span><span style="color:#222222">length</span><span style="color:#11796D">}</span><span style="color:#11796D"> characters from stream'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#222222"> }</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(</span><span style="color:#11796D">'file is now closed'</span><span style="color:#222222">);</span></span> <span class="line"><span style="color:#222222">} </span><span style="color:#D43324">catch</span><span style="color:#222222"> (e) {</span></span> <span class="line"><span style="color:#6200EE"> print</span><span style="color:#222222">(e);</span></span> <span class="line"><span style="color:#222222">}</span></span></code></pre></div></div><p>Use <code>utf8.encode()</code> to encode a Dart string as a list of UTF8-encoded bytes:</p> <?code-excerpt "misc/test/library_tour/convert_test.dart (utf8-encode)" replace="/ \/\/line-br.*//g"?> <div class="code-block-wrapper language-dart"><div class="code-block-body"><span class="code-block-language" title="Language dart">dart</span><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#0468D7">Uint8List</span><span style="color:#222222"> encoded = utf8.</span><span style="color:#6200EE">encode</span><span style="color:#222222">(</span><span style="color:#11796D">'Îñţérñåţîöñåļîžåţîờñ'</span><span style="color:#222222">);</span></span> <span class="line"></span> <span class="line"><span style="color:#D43324">assert</span><span style="color:#222222">(encoded.length == utf8Bytes.length);</span></span> <span class="line"><span style="color:#D43324">for</span><span style="color:#222222"> (</span><span style="color:#0468D7">int</span><span style="color:#222222"> i = </span><span style="color:#11796D">0</span><span style="color:#222222">; i < encoded.length; i++) {</span></span> <span class="line"><span style="color:#D43324"> assert</span><span style="color:#222222">(encoded[i] == utf8Bytes[i]);</span></span> <span class="line"><span style="color:#222222">}</span></span></code></pre></div></div><div class="header-wrapper"><h2 id="other-functionality">Other functionality</h2><a class="heading-link" href="#other-functionality" aria-label="Link to 'Other functionality' section">#</a></div><p>The dart:convert library also has converters for ASCII and ISO-8859-1 (Latin1). For details, see the <a href="https://api.dart.dev/dart-convert/dart-convert-library.html">API reference for the dart:convert library.</a></p><nav id="subnav"><ul><li class="previous"><a href="/libraries/dart-math">⟨ dart:math</a></li><li class="next"><a href="/libraries/dart-io">dart:io ⟩</a></li></ul></nav><p id="page-github-links"><span>Unless stated otherwise, the documentation on this site reflects Dart 3.5.4. 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