The cross-browser extension framework

Extension.js

• Create A New Extension — How to create a new extension.
• Get Started Immediately — Get work done in no time.
• Start From An Example — Start with your favorite tool.
• I have An Extension — Use only specific parts of Extension.js.

Extension.js makes it very easy to develop cross-browser extensions.
Developers prefer it for its fast builds, unified interface, and zero configuration setup.

Create A New Extension

Use the create command to generate a new extension. Also works with pnpm, yarn, and bun.

npx extension@latest create my-extension
cd my-extension
npm run dev

Watch Demo

create-a-new-extension.mp4

Web Standards and Framework Support

ESNext Try out	TypeScript Try out	WASM (soon)	React Try out	Vue Try out	Svelte Try out	Preact Try out

Get Started Immediately

Start developing an extension using a sample from Chrome Extension Samples

See the example below where we request the sample page-redder from Google Chrome Extension Samples.

Watch Demo

chrome-extension-sample-page-redder-on-edge.mp4

Try Yourself

npx extension@latest dev https://github.com/GoogleChrome/chrome-extensions-samples/tree/main/functional-samples/sample.page-redder --browser=edge

I have An Extension

If you have an existing extension which is using a package manager, you can install the Extension.js package and manually create the scripts used to run your extension.

See How It Works

usage-with-an-existing-extension.mp4

Step 1 - Install extension as a devDependency

npm install extension@latest --save-dev

Step 2 - Link your npm scripts with the executable Extension.js commands

{
  "scripts": {
    "build": "extension build",
    "dev": "extension dev",
    "preview": "extension preview"
  },
  "devDependencies": {
    // ...other dependencies
    "extension": "latest"
  }
}

Done. You are all set!

• To develop the extension, run npm run dev.
• To build the extension in production mode, run npm run build.
• To visualize the extension in production mode, run npm run build and npm run preview.

Using a specific browser for development

Chrome browser ✅	Edge browser ✅	Firefox browser ✅	Safari browser (soon)	Chromium-based ✅	Gecko-based ✅

Browser flags and custom binaries

Use these flags with extension dev, extension start, or extension preview:

• Select a browser: --browser <chrome | edge | firefox>
• Custom Chromium binary: --chromium-binary <path-to-binary>
• Custom Gecko (Firefox) binary: --gecko-binary <path-to-binary>

Examples:

# Chrome (system default)
npx extension@latest dev --browser=chrome

# Edge
npx extension@latest dev --browser=edge

# Custom Chrome/Chromium path
npx extension@latest dev --chromium-binary "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"

# Custom Firefox path
npx extension@latest dev --gecko-binary "/Applications/Firefox.app/Contents/MacOS/firefox"

Browser testing via

License

MIT (c) Cezar Augusto and the Extension.js Authors.