1. Add preload to dev_dependencies in pubspec.yaml. You should already have a dependency on build_runner.

     name: my_pkg
       build_runner: ^1.0.0
       preload: ^1.0.0
  2. Update the html in your web directory.

    1. Rename index.html to index.template.html.
    2. Add a place-holder for the preload entries.
       <script defer type="application/javascript" src="main.dart.js"></script>
  3. Run a build.

     > pub run build_runner build

    You should now see index.html generated with preloads defined.

       <link rel="preload" href="main.dart.js" as="script">
       <link rel="preload" href="assets/font.ttf" as="font" crossorigin>
       <link rel="preload" href="assets/image.jpg" as="fetch" crossorigin>
       <link rel="preload" href="assets/json.json" as="fetch" crossorigin>
       <link rel="preload" href="packages/pkg/assets/json.json" as="fetch" crossorigin>
       <script defer type="application/javascript" src="main.dart.js"></script>

build.yaml configuration

The builder also supports configuration values. Below are the supported keys along with their defaults.

debug: false
exclude: []
- 'web/**'
- 'lib/**'


Configuration for using package:build-compatible build systems.