Flutter WebMedium30 XP4 min read
What are the Flutter web renderers and when do you use each?
TL;DR: HTML renderer: smaller initial download, uses browser DOM/CSS, limited fidelity. CanvasKit: pixel-perfect rendering using WebAssembly + Skia, larger (~2MB) download. Flutter 3.22+ defaults to WASM with CanvasKit for best performance.
Full Answer
| Aspect | HTML renderer | CanvasKit (WASM) |
|---|---|---|
| Download size | ~1MB | ~2.5MB initial |
| Fidelity | Limited (browser CSS limits) | Pixel-perfect (Skia on WASM) |
| Performance | Uses browser compositing | Better for complex/animated UI |
| SEO | Some DOM output | No SEO value (canvas only) |
| Best for | Simple apps, SEO-important | Complex UI, design-critical apps |
🎯
Flutter 3.22+ uses 'auto' which picks HTML for mobile browsers and CanvasKit for desktop. For production, profile both — CanvasKit is usually better for apps, HTML for content sites.
Code Examples
bashSpecifying the web renderer
Output
// Auto mode: mobile web gets HTML, desktop gets CanvasKit
Common Mistakes
- ✗Using CanvasKit for a primarily text/content site — poor SEO and large download for no benefit
- ✗Expecting identical rendering between HTML renderer and CanvasKit — subtle font and shadow differences exist
Interview Tip
💡
Mention WASM as the future — Flutter 3.22 introduced Flutter WASM (WebAssembly) which eliminates the JS bridge overhead entirely and makes CanvasKit perform significantly faster.
#canvaskit#html-renderer#wasm#flutter-web