Welcome to the code repository for Flutter for web.
This repository contains the source code for a fork of Flutter that targets the web. Our goal is to add web support as a first-tier platform in the Flutter SDK alongside iOS and Android. The code in this repository is a stepping stone to that goal, providing web-only packages that implement (almost) the entire Flutter API.
Web support for Flutter is not yet stable. We're designating this release as a technical preview, designed to validate that the product meets developers' needs, iterate on major features and get to feature complete. Design and implementation may change significantly, and changes may be introduced that break compatibility with existing code. As a result, the Flutter team do not recommend using code created with Flutter for web in production at this time.
You can find a short introduction to Flutter for web on our blog.
We intend to completely support all of Flutter's API and functionality across modern browsers. However, during this preview, there are a number of exceptions:
flutter_web
does not have a plugin system yet. Temporarily, we provide
access to dart:html
, dart:js
, dart:svg
, dart:indexed_db
and other web
libraries that give you access to the vast majority of browser APIs. However,
expect that these libraries will be replaced by a different plugin API.flutter_web
may feel like a mobile app, even
when running on a desktop browser.Flutter for web provides:
When built with the production compiler, Flutter supports Chromium-based browsers and Safari, both on desktop and mobile. We also aim to fully support Firefox and Edge as targeted platforms, but our own test coverage is still low on these browsers. Our intention is to support the current and the last two major releases. Feedback on rendering and performance issues on all of these browsers is appreciated.
Internet Explorer support is not planned.
The development compiler currently supports Chrome only.
While we are far from code complete, we're ready for you to start developing and experimenting with Flutter for web. We are building the product around a number of target scenarios, as described in our blog, and we'd appreciate your feedback on feature gaps or suitability for these scenarios, as well as other scenarios for which you find Flutter useful on the web.
In addition, we'd love to see repros that demonstrate crashes, rendering fidelity issues or extreme performance issues. We'd also love general feedback on the quality of the release and the developer experience.
Of particular interest to us is testing across a variety of operating systems used for development (Windows, Linux, Mac) and browsers used for deployment.
Since we are developing this in a separate fork to the main Flutter repo, we are not yet ready to accept GitHub pull requests at this time. However, GitHub issues are very welcome.
Flutter 1.5 and above enable support for targeting the web with Flutter,
including Dart compilation to JavaScript. To use the Flutter SDK with the
flutter_web
preview make sure you have upgraded Flutter to at least v1.5.4
by running flutter upgrade
from your machine. If you're actively developing
for Flutter for web, you may prefer to be running from one of the unstable
channels. Our wiki describes the
Flutter channels
and how to select the right one for your needs.
Clone this repository locally.
To install the
webdev
package,
which provides the build tools for Flutter for web, run the following:
$ flutter packages pub global activate webdev
Ensure that the $HOME/.pub-cache/bin
directory
is in your path,
and then you may use the webdev
command directly from your terminal.
The example exists at examples/hello_world
in the repository.
$ cd examples/hello_world/
Update packages.
$ flutter packages upgrade
! flutter_web 0.0.0 from path ../../flutter_web
! flutter_web_ui 0.0.0 from path ../../flutter_web_ui
Running "flutter packages upgrade" in hello_world... 5.0s
If that succeeds, you're ready to run it!
Build and serve the example locally.
$ webdev serve
[INFO] Generating build script completed, took 331ms
...
[INFO] Building new asset graph completed, took 1.4s
...
[INFO] Running build completed, took 27.9s
...
[INFO] Succeeded after 28.1s with 618 outputs (3233 actions)
Serving `web` on http://localhost:8080
Open http://localhost:8080 in Chrome and you should see Hello World
in
red text in the upper-left corner.
Visual Studio Code supports Flutter web development with the v3.0 release of the Flutter extension.
Flutter: New Web Project
command from VS Codewebdev
command-line tool to build and run your app; a
new Chrome window should open, showing your running apppub get
will be run automaticallyrun
button on the main toolbarwebdev
command-line tool to build and run your app; a
new Chrome window should open, showing your running appIf you'd like to depend on the flutter_web
packages without cloning the
repository, you can setup your pubspec as follows:
name: my_flutter_web_app
environment:
sdk: '>=2.2.0 <3.0.0'
dependencies:
flutter_web: any
flutter_web_ui: any
dev_dependencies:
# Enables the `pub run build_runner` command
build_runner: ^1.1.2
# Includes the JavaScript compilers
build_web_compilers: ^1.0.0
# flutter_web packages are not published to pub.dartlang.org
# These overrides tell the package tools to get them from GitHub
dependency_overrides:
flutter_web:
git:
url: https://github.com/flutter/flutter_web
path: packages/flutter_web
flutter_web_ui:
git:
url: https://github.com/flutter/flutter_web
path: packages/flutter_web_ui
webdev
To use webdev
with hot-reload, run the following within your project
directory:
$ webdev serve --auto restart
You'll notice a similar output to flutter packages pub run build_runner serve
but now changes to your application code should cause a quick refresh of the
application on save.
Note: the
--hot-reload
option is not perfect. If you notice unexpected behavior, you may want to manually refresh the page.
Note: the
--hot-reload
option is currently "stateless". Application state will be lost on reload. We do hope to offer "stateful" hot-reload on the web – we're actively working on it!
The workflow documented above (available with build_runner
and webdev
) uses
the Dart Dev Compiler which is
designed for fast, incremental compilation and easy debugging.
If you'd like evaluate production performance, browser compatibility and code size, you can enable our release compiler, dart2js.
To enable the release compiler, pass in the --release
flag (or just -r
).
$ webdev serve -r
Note: Builds may be slower in this configuration.
If you'd like to generate output to disk, we recommend you use webdev
.
$ webdev build
This will create a build
directory with index.html
, main.dart.js
and the
rest of the files needed to run the application using a static HTTP server.
To optimize the output JavaScript, you can enable optimization flags using a
build.yaml
file in the root of your project with the following contents:
# See https://github.com/dart-lang/build/tree/master/build_web_compilers#configuration
targets:
$default:
builders:
build_web_compilers|entrypoint:
generate_for:
- web/**.dart
options:
dart2js_args:
- --no-source-maps
- -O4
Note: the
-O4
option enables a number of advanced optimizations that may cause runtime errors in code that has not been thoroughly tested.
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