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Plug-and-play, zero-config, cross-browser extension development tool.

Screenshot 2024-03-25 at 13 06 15


Create cross-browser extensions with no build configuration.

extension is a plug-and-play, zero-config, cross-browser extension development tool with built-in support for TypeScript, WebAssembly, React, and modern JavaScript.

Create A New Extension

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

A new browser instance will open up with your extension ready for development.

You are done. Time to hack on your extension!


Get Started Immediately

Kickstart Any Sample from Chrome Extension Samples

Dive right into development by starting with a sample from the Chrome Extension Samples repository. It's a great way to get acquainted with best practices and save time:

  1. Open your terminal.
  2. Navigate to the directory where you want your project.
  3. Run the command:
    npx extension dev <sample-name>
    Replace <sample-name> with the name of the sample you wish to use from Chrome Extension Samples.

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


Use Microsoft Edge to kickstart any sample from chrome-extesions-sample

extension supports a variety of browsers, including Microsoft Edge. To start an Edge-compatible extension, simply:

  1. Open your terminal.
  2. Navigate to your desired project directory.
  3. Execute:
    npx extension dev  <sample-name> --browser=edge
    Tailor your command by replacing <sample-name> with the specific sample you're interested in.

See the example below where we request the sample magic8ball from from Google Chrome Extension Samples using Edge as the runtime browser.

npx extension dev https://github.com/GoogleChrome/chrome-extensions-samples/tree/main/api-samples/topSites/magic8ball --browser=edge


Run Mozilla Add-Ons Using Edge

Bridge the gap between Firefox and Edge by running Mozilla Add-Ons using Edge:

  1. Navigate to your project directory.
  2. Use the command:
    npx extension dev <addon-name> --browser=edge --polyfill=true 
    This will fetch a Mozilla Add-On and adapt it for Edge.

See the example below where we request the sample Apply CSS from MDN WebExtensions Examples using Edge as the runtime browser.

npx extension dev https://github.com/mdn/webextensions-examples/tree/main/apply-css --browser=edge --polyfill=true


I have An Extension


If you have an existing extension which is using a package manager, you can install the extension package and manually create the scripts used to run your extension. See the demo above or follow these instructions to get it done:

Step 1 - Install extension as a devDependency

npm install extension --save-dev

Step 2 - Link your npm scripts with the executable extension commands

  "scripts": {
    "build": "extension build",
    "dev": "extension dev",
    "start": "extension start"
  "devDependencies": {
    // ...other deps,s
    "extension": "latest"

Done. You are all set!

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

Using a specific browser for development

Desktop Browsers

☑️ = Likely works but no browser runner support yet.

Brave Browser Google Chrome Microsoft Edge Mozilla Firefox Opera Browser Vivaldi Browser

If you want to target a specific browser, just pass the --browser flag to the dev/start command (based on the list available above), like npx extension dev path/to/extension --browser=edge.

Hint Pass --browser="all" to load all available browsers at once.

extension dev --browser=all

Screenshot 2024-03-25 at 13 06 15


MIT (c) Cezar Augusto.

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