Flutter Web - What is it & How Does it Work?
Unlike traditional web frameworks, Flutter Web doesn't rely on standard HTML elements. Instead, it uses its own rendering engine to make your app run smoothly in web browsers.
Custom Rendering Engine
Flutter web doesn't use traditional web technologies like HTML, CSS or the DOM (Document Object Model) for rendering. Instead, it uses its own CanvasKit renderer in combination with WebGL to draw every single pixel on the screen.
This all can be done by first compiling everything to WebAssembly (WASM), which has multiple benefits like improved speed and smaller file size.
Side note: In the past, Flutter offered different rendering options for the web. However, as of recent updates, Flutter Web now exclusively uses the CanvasKit renderer.
Rendering components
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🌐 Flutter Web
Used by developers to build their actual app, using the Dart language and Flutter’s UI framework. It handles widget composition, state management, app logic, and layout at a high level.
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⚙️ Compilation to JavaScript
The Dart code is compiled into JavaScript via dart2js or dartdevc (for debug builds). This enables the app to run in browser, which doesn't support Dart directly.
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🖼 CanvasKit Renderer
Flutter Web’s high-performance renderer. It's a webAssembly-compiled port of Skia and converts Flutter’s paint commands into low-level drawing instructions.
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🧱 Skia
A fast, cross-platform 2D graphics library originally written in C++. In the web version, it's compiled to WASM and used within CanvasKit.
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🧩 WebAssembly (WASM)
A binary instruction format that allows native-like performance in the browser. It enables Skia to run efficiently within the browser environment (via CanvasKit).
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🎮 WebGL
A browser-based graphics API that draws the UI on an
<canvas>element. Used by CanvasKit to render graphics with hardware acceleration.
Rendering steps
- Dart code is written in Flutter Web.
- The Dart code compiles to JavaScript.
- JavaScript interacts with CanvasKit (the WASM-based rendering engine).
- CanvasKit, using Skia logic compiled into WASM, prepares drawing instructions.
- These instructions are rendered using WebGL onto the screen via
<canvas>.
TLDR: Flutter Web compiles your code into fast, browser-friendly JavaScript. It uses a powerful graphics engine under the hood to draw everything efficiently. The result feels just as responsive as a native app, without the need for any extra steps.
Single Page Application
Flutter Web functions as a Single Page Application (SPA), meaning it loads a single HTML page and dynamically updates the content without requiring a full-page refresh. This is similar to JavaScript frameworks like React, Angular, and Vue.
When a Flutter Web app is opened, the entire application is compiled into WebAssembly, allowing it to run efficiently in the browser.
Instead of traditional DOM-based rendering, Flutter Web loads an HTML shell containing a <canvas> element, where the framework renders the UI.
This makes everything feel smooth and responsive.
Consistency Across Platforms
One of the best things about Flutter is that it looks and feels the same on all platforms. The same rendering logic works everywhere, so you get a consistent user interface.
Benefits of Using Flutter for Web
🚀 Speed (once loaded)
After the initial loading period, Flutter Web applications are really performant. Interactions, animations, and state updates feel responsive and smooth due to Flutter's efficient rendering engine.
Since it operates as a Single Page Application, it dynamically updates the UI without requiring full-page reloads, further improving the user experience.
🔄 Reuses mobile code
The biggest advantage is code reusability. If you also want to built a Flutter mobile app, you can share up to 90% of your codebase when extending to the web. This significantly reduces development time and maintenance costs.
🎨 Smooth user experience
Flutter Web excels at creating polished applications that look and feel like the real deal. It handles complex UI, state management, and transitions with minimal effort, providing a great user experience similar to native applications.
Downsides
🔍 Not the best for SEO
Because Flutter Web doesn't generate standard HTML content, search engines struggle to index Flutter websites properly. This makes it a poor choice for content-focused websites that rely on search traffic.
In general, Flutter Web isn't meant for building marketing websites or other SEO-dependent apps like blogs. Instead, it excels at creating complex web applications like admin dashboards, internal tools, enterprise software or other tools that require extensive user interaction and display dynamic data.
⌛ Initial loading time
Flutter Web traditionally loads slower than conventional websites because it must first download and initialize its entire rendering engine before displaying content. However, by 2025, significant improvements have dramatically reduced this gap through WebAssembly optimization, more efficient code splitting, and a improved architecture.
🐛 Different debugging tools
Debugging can be challenging because of it's custom rendering engine instead. You can't just inspect a web page and select the specific HTML fields. This makes traditional web debugging tools often don't work well with Flutter.
To resolve this, Flutter offers specific DevTools for better profiling capabilities and enhanced IDE plugins to help detect issues.
🗄️ No SSR (Server-Side Rendering)
Flutter Web can't render pages on the server, which hurts SEO and makes initial loading slower. Developers have found clever workarounds using custom solutions that create search-friendly content before the app fully loads. While these fixes help, they're not as smooth as the built-in server rendering that other web frameworks offer.
👤 Harder to find devs, or is it?
Finding Flutter developers was once difficult compared to hiring for established web frameworks. This gap is closing as Flutter's popularity and adoption grows and more developers add it to their skillset.
Dart, Flutter's programming language, is relatively easy to learn, especially for those familiar with JavaScript or other object-oriented languages. Flutter is easy to get started with. It has a helpful community, with great docs to help if you get stuck.
When to Use It
✅ Admin dashboards
Flutter Web is perfect for web applications where nobody cares about Google rankings. Need complex tables, fancy charts, and lots of user controls? Flutter handles these beautifully. These app solve user's problems, so the extra few seconds of loading isn't a big deal.
✅ Mobile & web apps
Want your app to work on phones and browsers without building everything twice? Flutter lets you reuse most of your code across platforms. Your app looks the same everywhere, and you'll save months of development time not rebuilding features.
Many developers are surprised by how quickly they can build stuff once they get the hang of Flutter. It feels different from traditional web development at first, but that "aha moment" comes pretty quickly.
Future of Flutter Web
As of 2025, Flutter Web has seen significant improvements, addressing many of the challenges it faced in earlier.
- Support & Updates: Google continues to invest heavily in Flutter, with regular updates addressing web-specific issues. This ongoing support ensures Flutter Web remains stable and continues to mature.
- SEO Improvements: The community has developed workarounds like serverless functions and edge rendering to improve search engine accessibility. While these solutions aren't officially supported by Flutter, they help enhance SEO capabilities. The Flutter team continues to explore improvements.
- Initial Loading Time Optimizations: Exclusive use of WebAssembly (WASM), tree shaking, lazy loading techniques, and Progressive Web Apps (PWAs) support have all contributed to faster load times and better performance.
Google continues to heavily invest in Flutter Web, with regular updates and growing adoption by major companies proving it's a strategic platform for the future, not an experiment they'll abandon.