flutter · kevmoo · Aug 4, 2026 · Aug 4, 2026 · Aug 4, 2026 · Aug 4, 2026
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+---
+title: "Try Flutter Web with WebAssembly Week"
+description: >-
+  Unlock up to 2x to 5x faster web performance by opting into Wasm compilation today
+publishDate: 2026-08-17
+author: kevmoo
+image: images/header_placeholder.webp
+category: event
+layout: blog
+---
+
+<!-- TODO(graphics): Replace with finalized banner artwork featuring Dash and WebAssembly branding -->
+<DashImage figure src="images/header_placeholder.webp" alt="Dash celebrating Try Flutter Web with WebAssembly Week" caption="Welcome to Try Flutter Web with WebAssembly Week" />
+
+Flutter lets you build expressive, multi-platform apps for the web from a
+single codebase. Whether you're building a dashboard, a tool for your team, or
+a full web application, Flutter Web gives you the power to bring your app to
+any browser.
+
+From August 17 to August 21, we're hosting **Try Flutter Web with WebAssembly
+Week**! Throughout the week, Dart and Flutter engineers will triage incoming
+issues in real time to help unblock migrations, and our developer relations team
+will share your wins across community channels.
+
+---
+
+## WebAssembly in Flutter Web
+
+We stabilized WebAssembly (Wasm) support in Flutter 3.22 back in May 2024 by
+pairing the Dart compiler with WebAssembly Garbage Collection (WasmGC).
+
+Since then, Wasm compilation has proven itself on real-world apps. For
+example, **Dart DevTools** (`dartdevtools`)—a complex, highly interactive
+Flutter web app—has shipped with WebAssembly by default since late 2024.
+Today, over 97% of developers using DevTools run it on Wasm, benefiting from
+smooth UI inspection, fast loading, and rock-solid stability.
+
+Wasm compilation is battle-tested and production-ready. In fact, our analysis
+shows that **over 58% of existing Flutter web apps compile to WebAssembly
+today with zero code changes**.
+
+When you compile to WebAssembly, your app benefits from both compiler
+acceleration (`dart2wasm`) and multithreaded rendering (`skwasm`):
+
+*   ⚡ **Up to 2x faster frame times & sustained 60 FPS**: Under heavy widget
+    tree churn where JavaScript drops frames down to ~30 FPS (34.5 ms total
+    frame time), Wasm maintains smooth 60 FPS delivery (17.4 ms total frame
+    time).
+*   ⚡ **Up to 2.5x faster widget building & execution**: Native WasmGC
+    structures accelerate complex UI logic and state updates, cutting widget
+    build time from 29.3 ms down to 11.4 ms.
+*   ⚡ **Multithreaded background rasterization**: Skwasm offloads canvas
+    rasterization to a dedicated Web Worker, keeping the main browser thread
+    free for responsive UI interactions.
+*   🎯 **Over 3x smoother frame consistency**: Cuts frame jitter from
+    ±1.5 ms down to ±0.5 ms, eliminating garbage collection pauses.
+*   📦 **Minimal bundle size change**: Total application bundle size is no
+    more than 5% larger compressed over the wire.
+
+<!-- TODO(graphics): Replace with finalized artwork if updated by design -->
+<DashImage figure src="images/perf_comparison_placeholder.webp" alt="WebAssembly versus JavaScript framerate and performance comparison" caption="Live performance comparison on flutter-wasm-compare.web.app: WebAssembly delivers 2.0x faster total frame times (17.4ms vs 34.5ms), 2.5x faster widget build speeds (11.4ms vs 29.3ms), and 3.0x lower jitter." />
+
+Try it yourself! You can test and compare performance on your own hardware
+using our interactive demo at
+[flutter-wasm-compare.web.app](https://flutter-wasm-compare.web.app/)
+([source code](https://github.com/kevmoo/flutter-wasm-compare)).
+
+*Benchmark metrics above measured in Google Chrome 151 (151.0.7922.109) on an
+Apple M4 Pro MacBook Pro (48 GB, macOS Sequoia 15.7.7) at a 60 Hz display
+refresh cap under medium stress (200 animated churn nodes).*
+
+---
+
+## Why JavaScript is still the default compiler target
+
+If Wasm delivers better speed and stability, why does `flutter build web`
+still default to JavaScript (`dart2js`)?
+
+Changing the default compiler for millions of developers is a big move. While
+over half of Flutter web apps build with Wasm out of the box, some `pub.dev`
+packages still rely on legacy JavaScript interop (`dart:html` or `dart:js`)
+that needs to be updated for Wasm compatibility.
+
+This creates a classic chicken-and-egg dilemma:
+* We can't make `--wasm` the default until more ecosystem packages update
+  their JS interop code.
+* Package authors often don't prioritize updating until developers opt in to
+  Wasm and request Wasm support.
+
+---
+
+## WebAssembly migration resources
+
+To help you migrate, we've updated our web documentation. Check out these
+guides before building:
+
+*   **[WebAssembly on Flutter Web](https://docs.flutter.dev/platform-integration/web/wasm)**:
+    Learn how to set server headers (`COEP: credentialless` and `COOP:
+    same-origin`), debug production builds, and detect Wasm support at runtime.
+*   **[Migrating to `package:web` and modern JS interop](https://dart.dev/interop/js-interop)**:
+    Moving away from `dart:html` and `dart:js` is key for Wasm compatibility.
+    This guide shows how to migrate to `package:web` and `dart:js_interop`.
+*   **[Web building and deployment guide](https://docs.flutter.dev/deployment/web)**:
+    Find instructions for release builds, source maps, Firebase Hosting, and CDN
+    caching.
+*   **[Flutter web technical FAQ](https://docs.flutter.dev/platform-integration/web/faq)**:
+    Get answers about web workers, service workers, and conditional imports.
+
+---
+
+## Try WebAssembly this week
+
+Whether you maintain a `pub.dev` package, manage a production web app, or
+build side projects, test your code with WebAssembly this week!
+
+### How to get started
+1.  **Upgrade to Flutter 3.47:** Run `flutter upgrade` to ensure you're on
+    the latest stable release with our newest WasmGC optimizations and runtime
+    fixes.
+2.  **Build with Wasm:** Run `flutter build web --wasm` in your project
+    terminal.
+3.  **Report any blockers:** If you run into package dependencies or runtime
+    issues, let us know! File a report at
+    👉 **[https://goo.gle/flutter-wasm-feedback](https://goo.gle/flutter-wasm-feedback)**
+    so our engineers can help unblock migration.
+4.  **Share your wins:** If your app builds cleanly and runs faster, tell us!
+    Share your before-and-after metrics or framerate gains at
+    👉 **[https://goo.gle/flutter-web-wasm-win](https://goo.gle/flutter-web-wasm-win)**.
+
+When posting on social media, use **`#FlutterWasmWeek`** so we can feature
+your results!
+
+---
+
+## Building a Wasm-by-default web future
+
+By testing your apps and resolving package dependencies together this week,
+we can pave the way to making **WebAssembly the default compiler for Flutter
+Web**.
+
+Run `flutter upgrade`, try `flutter build web --wasm`, and let us know how it
+goes!