why flutter web release load take time

Why Flutter Web Release Loads Slowly

1. Big JS Bundle
   • Flutter compiles your Dart code into JavaScript (main.dart.js).
   • This file can be 5–10 MB (or more if you use many packages).
   • First-time users must download this entire file.
2. CanvasKit Rendering
   • By default, Flutter Web uses CanvasKit (a WebAssembly engine for drawing).
   • The CanvasKit WASM + fonts + JS adds a few MB extra.
   • First load = slow, but cached later.
3. Fonts & Assets
   • Custom fonts and images increase load time.
   • Flutter embeds fonts into the app.
4. No Code-Splitting
   • Unlike React/Angular, Flutter bundles everything into one big JS file.
   • Even if you only need a small page, the whole app must load.
5. Hosting/Server Speed
   • If you’re hosting on slow servers (or no CDN), the download is slower.
   • On free hosting (like GitHub Pages), initial load may be 5–10 sec.

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How to Improve Load Speed

1. Use --release build (already does optimizations) flutter build web --release
2. Enable Tree Shaking for Icons
   If you use material icons: flutter build web --release --pwa-strategy=offline-first Or add to pubspec.yaml: flutter: uses-material-design: true This removes unused icons.
3. Use WebRenderer = html (lighter but less accurate graphics) flutter build web --release --web-renderer html
   • html: smaller, faster load, but less accurate animations.
   • canvaskit: better quality, heavier.
4. Compress Assets & Fonts
   • Use only required fonts.
   • Convert PNG → WebP.
   • Remove unused assets.
5. Enable GZIP/Brotli Compression on Server
   • If hosting on Nginx/Apache/Cloudflare, enable compression.
   • Reduces JS size by 70%+.
6. Host on a CDN (Firebase Hosting, Vercel, Netlify)
   • Faster delivery worldwide.
   • Built-in caching.
7. Use Service Worker (PWA)
   • Offline-first caching makes subsequent loads instant.

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First-time load will always be slower (user must download ~2–6 MB).
But with compression + html renderer + caching, you can make it 2–3 sec even on average internet.