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repositories</span></div></a></li></ul></li><li class="nav-item"><a class="nav-link" href="/tools/pub/private-files"><div><span>What not to commit</span></div></a></li></ul></li><li class="nav-item"><button class="nav-link active collapsible" data-toggle="collapse" data-target="#-sidenav-5" role="button" aria-expanded="true" aria-controls="-sidenav-5"><span>Development</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse show" id="-sidenav-5"><li class="nav-item"><a class="nav-link" href="/libraries/serialization/json"><div><span>JSON serialization</span></div></a></li><li class="nav-item"><a class="nav-link" href="/resources/language/number-representation"><div><span>Number representation</span></div></a></li><li class="nav-item"><a class="nav-link" href="/resources/google-apis"><div><span>Google APIs</span></div></a></li><li class="nav-item"><a class="nav-link" href="/multiplatform-apps"><div><span>Multi-platform apps</span></div></a></li><li class="nav-item"><button class="nav-link collapsible collapsed" data-toggle="collapse" data-target="#-sidenav-5-5" role="button" aria-expanded="false" aria-controls="-sidenav-5-5"><span>Command-line & server apps</span> <span class="material-symbols expander" aria-hidden="true">expand_more</span></button><ul class="nav collapse" id="-sidenav-5-5"><li class="nav-item"><a class="nav-link" href="/server"><div><span>Overview</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/get-started"><div><span>Get started</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/cmdline"><div><span>Write command-line apps</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/fetch-data"><div><span>Fetch data from the internet</span></div></a></li><li class="nav-item"><a class="nav-link" href="/tutorials/server/httpserver"><div><span>Write HTTP servers</span></div></a></li><li 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class="site-toc__title">Contents</header><ul class="section-nav"><li class="toc-entry nav-item"><a class="nav-link" href="#webassembly-support">WebAssembly support</a><ul class="nav"><li class="toc-entry nav-item"><a class="nav-link" href="#supported-packages">Supported packages</a></li></ul></li><li class="toc-entry nav-item"><a class="nav-link" href="#compiling-to-wasm">Compiling your web app to Wasm</a></li></ul></div><article><div class="content"><div id="site-content-title"><h1>WebAssembly (Wasm) compilation</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="#webassembly-support">WebAssembly support</a><ul><li class="toc-entry"><a href="#supported-packages">Supported packages</a></li></ul></li><li class="toc-entry"><a href="#compiling-to-wasm">Compiling your web app to Wasm</a></li></ul></div><p>The Dart team is excited to add <a href="https://webassembly.org/">WebAssembly</a> as a compilation target when building Dart and <a href="https://flutter.dev/wasm">Flutter</a> applications for the web.</p><p>Development of WebAssembly support remains ongoing, which will potentially result in frequent changes. Revisit this page for the latest updates.</p><aside class="alert alert-info"><div class="alert-header"><span class="material-symbols" aria-hidden="true">info</span> <span>Note</span></div><div class="alert-content"><p><strong>Support for Wasm is now in stable!</strong></p><p>WebAssembly support for Dart web is available on the Dart <em>stable</em> <a href="/get-dart#release-channels">channel</a>.</p></div></aside><div class="header-wrapper"><h2 id="webassembly-support">WebAssembly support</h2><a class="heading-link" href="#webassembly-support" aria-label="Link to 'WebAssembly support' section">#</a></div><p>The current version of Dart compilation to WebAssembly has a number of restrictions:</p><ol><li><p>It targets WebAssembly with Garbage Collection (<a href="https://developer.chrome.com/blog/wasmgc/">WasmGC</a>), so not all browsers are currently supported. The current list of browsers is available in the <a href="https://flutter.dev/wasm">Flutter documentation</a>.</p></li><li><p>The compiled Wasm output currently targets JavaScript environments (such as browsers), and thus currently doesn't support execution in standard Wasm run-times like wasmtime and wasmer. For details, see <a href="https://github.com/dart-lang/sdk/issues/53884">issue #53884</a></p></li><li><p>Only Dart's <a href="/interop/js-interop/">next-gen JS interop mechanism</a> is supported when compiling to Wasm.</p></li><li><p>There is currently no support in the <code>webdev</code> tool for running (<code>webdev serve</code>) or building (<code>webdev build</code>). The steps below contain a temporary workaround. For details, see <a href="https://github.com/dart-lang/webdev/issues/2296">webdev issue 2206</a>.</p></li></ol><div class="header-wrapper"><h3 id="supported-packages">Supported packages</h3><a class="heading-link" href="#supported-packages" aria-label="Link to 'Supported packages' section">#</a></div><p>To find Wasm-compatible packages, use the <a href="https://pub.dev/packages?q=is%3Awasm-ready"><code>wasm-ready</code></a> filter on <a href="https://pub.dev">pub.dev</a>.</p><p>A package is "wasm-ready" if it doesn't import non-Wasm compliant libraries like <code>dart:html</code>, <code>dart:js</code>, etc. You can find the full list of unallowed libraries on the <a href="/interop/js-interop/#next-generation-js-interop">JS interop page</a>.</p><div class="header-wrapper"><h2 id="compiling-to-wasm">Compiling your web app to Wasm</h2><a class="heading-link" href="#compiling-to-wasm" aria-label="Link to 'Compiling your web app to Wasm' section">#</a></div><p>We've landed support in the <code>dart</code> CLI for invoking the Wasm compiler in Dart and <a href="https://flutter.dev/wasm">Flutter</a>:</p><div class="code-block-wrapper language-console"><div class="code-block-body"><pre class="shiki dash-light" tabindex="0"><code><span class="line"><span style="color:#222222">$ dart help compile wasm</span></span> <span class="line"><span style="color:#222222">Compile Dart to a WebAssembly/WasmGC module.</span></span> <span class="line"></span> <span class="line"><span style="color:#222222">Usage: dart compile wasm [arguments] <dart entry point></span></span> <span class="line"><span style="color:#222222">-h, --help Print this usage information.</span></span> <span class="line"><span style="color:#222222">-o, --output Write the output to <file name>.</span></span> <span class="line"><span style="color:#222222"> This can be an absolute or relative path.</span></span> <span class="line"><span style="color:#222222">-v, --verbose Print debug output during compilation</span></span> <span class="line"><span style="color:#222222"> --enable-asserts Enable assert statements.</span></span> <span class="line"><span style="color:#222222">-D, --define=<key=value> Define an environment declaration. To specify multiple declarations, use multiple</span></span> <span class="line"><span style="color:#222222"> options or use commas to separate key-value pairs.</span></span> <span class="line"><span style="color:#222222"> For example: dart compile wasm -Da=1,b=2 main.dart</span></span></code></pre></div></div><p>Wasm compilation is available in stable, but still in preview. While we continue optimizing tooling to improve developer experience, you can try compiling Dart to Wasm today by following the temporary steps outlined here:</p><ol><li><p>Start with a web app: <code>dart create -t web mywebapp</code></p><p>The template creates a small web app using <a href="https://pub.dev/packages/web"><code>package:web</code></a>, which is necessary to run Wasm. Make sure your web apps are <a href="/interop/js-interop/package-web/">migrated</a> from <code>dart:html</code> to <code>package:web</code>.</p></li><li><p>Compile with Wasm to a new <code>site</code> output directory: <code>mywebapp$ dart compile wasm web/main.dart -o site/main.wasm</code></p></li><li><p>Copy over the web files: <code>cp web/index.html web/styles.css site/</code></p></li><li><p>Create a JS bootstrap file to load the Wasm code:</p><p>Add a new file <code>site/main.dart.js</code> and fill it with the contents of this <a href="https://gist.github.com/mit-mit/0fcb1247a9444b0cadf611aa5fc6f32e"><code>main.dart.js</code> sample</a>.</p></li><li><p>Serve the output: <code>dart pub global run dhttpd</code> (<a href="https://pub.dev/packages/dhttpd">docs</a>)</p></li></ol><p>You can also try out this small example <a href="https://github.com/mit-mit/sandbox">here</a>.</p><p id="page-github-links"><span>Unless stated otherwise, the documentation on this site reflects Dart 3.7.1. Page last updated on 2024-06-17.</span> <a href="https://github.com/dart-lang/site-www/tree/main/src/content/web/wasm.md" target="_blank" rel="noopener">View source</a> <span>or </span><a href="https://github.com/dart-lang/site-www/issues/new?template=1_page_issue.yml&page-url=https://dart.dev/web/wasm/&page-source=https://github.com/dart-lang/site-www/tree/main/src/content/web/wasm.md" title="Report an issue with this page" target="_blank" rel="noopener">report an issue</a>.</p></div></article></main></div><footer id="page-footer"><div class="footer-section footer-main"><a href="/" class="brand" title="Dart"><img src="/assets/img/logo/logo-white-text.svg" alt="Dart" width="164"></a><div class="footer-social-links"><a href="https://medium.com/dartlang" target="_blank" rel="noopener" title="Dart's Medium publication"><svg><use href="/assets/img/social/medium.svg#medium"></use></svg> </a><a href="https://github.com/dart-lang" target="_blank" rel="noopener" title="Dart's GitHub organization"><svg><use href="/assets/img/social/github.svg#github"></use></svg> </a><a href="https://bsky.app/profile/dart.dev" target="_blank" rel="noopener" title="Dart's Bluesky profile"><svg><use href="/assets/img/social/bluesky.svg#bluesky"></use></svg> </a><a href="https://twitter.com/dart_lang" target="_blank" rel="noopener" title="Dart's X (Twitter) profile"><svg><use href="/assets/img/social/x.svg#x"></use></svg></a></div></div><div class="footer-section footer-tray"><div class="footer-licenses">Except as otherwise noted, this site is licensed under a <a href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution 4.0 International License</a>, and code samples are licensed under the <a href="https://opensource.org/licenses/BSD-3-Clause">3-Clause BSD License</a>.</div><div class="footer-utility-links"><ul><li><a href="/terms" title="Terms of use">Terms</a></li><li><a href="https://policies.google.com/privacy" target="_blank" rel="noopener" title="Privacy policy">Privacy</a></li><li><a href="/security" title="Security philosophy and practices">Security</a></li></ul></div></div></footer></div></body></html>