Flutter Web extends the Flutter framework to build web applications. You write the same Dart/Flutter code and compile it to JavaScript, running in browsers. Google, Google Ads, and Alibaba run Flutter Web in production. It enables code sharing: ship the same app to iOS, Android, and web from one codebase. Flutter Web renders via HTML/CSS or CanvasKit (GPU-accelerated). HTML mode is smaller and more compatible; CanvasKit is faster but larger (~10MB). Most apps use HTML mode for production.