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 A Template — 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 use it due to its fast builds, simple interface, and zero-configuration setup.

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

For a preview of extensions running these technologies, see the templates website.

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

👋 = PR Welcome!

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

npx extension 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 --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 ✅	Chromium ☑️	Edge ✅	Firefox ✅	Opera ☑️	Safari ⛔️

The browsers listed above represent those with official extension stores. Note that Chromium-based browsers (like Arc, Brave, Vivaldi, and many others) are theoretically supported through the Chrome/Chromium compatibility layer.

Firefox (Android) ⛔️	Safari (iOS) ⛔️

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