The cross-browser extension framework

• 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.

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

ESNext latest	TypeScript latest	WASM latest	React 18+	Vue 3+	Svelte 5+	Preact 10+	Angular 👋	Solid 👋

👋 = PR Welcome!

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.

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

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.

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.

Chrome browser ✅	Edge browser ✅	Firefox browser ✅	Opera browser ☑️	Safari browser ❌	Chromium-based ☑️	Gecko-based ☑️	Firefox (Android) ❌	Safari (iOS) ❌

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"

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