Flutter for Web: Build and Deploy
Flutter for Web compiles your Dart code into a web app. Use flutter build web and choose a renderer: HTML for smaller size or CanvasKit for performance. The footgun is the initial download size, which can be large and slow down first-page load.
Why it exists
Flutter for Web was created to enable developers to use a single Dart codebase to build applications for mobile, desktop, and the web. This reduces development time and helps maintain a consistent user experience across all platforms without writing a separate web application from scratch.
The mental model
Think of Flutter for Web not as embedding a mobile app in a browser, but as a compiler that translates your Flutter widgets and logic into standard web technologies. It creates a complete, client-rendered single-page application (SPA) from your existing Dart code, ready to be hosted on any static web server.
How it works
When you run the flutter build web command, the tool compiles your Dart code into JavaScript. It then packages this with a rendering engine and your app's assets into a build/web directory. You must choose a renderer using the --web-renderer flag. The html renderer uses a combination of HTML, CSS, and Canvas elements, resulting in a smaller download size. The canvaskit renderer uses WebAssembly (Wasm) to run the Skia graphics engine directly in the browser, offering higher fidelity and performance that's closer to native mobile, but at the cost of a significantly larger initial download.
When to use it
Use Flutter for Web when you want to deploy an existing Flutter application to a browser, reaching a wider audience without maintaining a separate web codebase. It is ideal for highly interactive applications, internal tools, dashboards, and companion web apps where cross-platform consistency is more important than SEO or the absolute fastest initial load time.
When not to use it
Avoid Flutter for Web for content-heavy, static websites that rely on search engine optimization (SEO). As a single-page app, its content is not easily crawlable by search engines. Also, if a minimal initial load time is a critical requirement for a public-facing site, the download size of the Flutter engine and app code can be a significant drawback.
One canonical example
To build your app for the web using the high-performance CanvasKit renderer, you run the command: flutter build web --web-renderer canvaskit. This generates a build/web directory containing all the necessary files (index.html, main.dart.js, assets, etc.). You can then deploy this directory to any static web hosting service like Firebase Hosting, Netlify, or GitHub Pages.
Interview question
Which Flutter web renderer is best suited when the primary concern is minimizing the initial download size of the application?
- a.HTML, as it utilizes standard browser rendering capabilitiesCorrect
- b.CanvasKit, due to its superior graphical fidelity
- c.Skia, for its direct hardware acceleration
- d.WebAssembly, because it offers faster execution
Why? this is the answer
The card states that the HTML renderer results in a "smaller download size" by using standard web elements. CanvasKit, while offering higher performance, comes "at the cost of a significantly larger initial download" because it uses WebAssembly and the Skia graphics engine.
Just read this? Test yourself on what you have been reading.
Read the original → docs.flutter.dev
Put your scrolling time to good use
Learn one idea, try a quiz and save useful cards for revision. Tezvyn makes it easy to learn and stay current in your tech field, a few minutes at a time.
The iPhone app is on the way
We are building it. Until it lands, nothing here is held back from you: every interview card, your saved cards, streaks and the job board all work in Safari, plus hundreds of free practice quizzes of thirty questions each. Sign in and it all carries over to the app the day it arrives.
Want it as an icon? Tap Share at the bottom of Safari, then Add to Home Screen. It opens full screen and the cards you have read stay available offline.
We are hiring for this. Open roles that interview on flutter — each one lists the topics its interview covers.
See open roles