Environment Variables

!Powered by Extension.js

TypeScript New Tab Example

Replaces your new tab page with a page showing the extension's environment values.

What you'll see: A custom new-tab page replacing the browser default.

How it works: The manifest overrides the new-tab page and loads a TypeScript entry bundled from src/newtab/.

Reads variables from .env at build time. Variables prefixed with EXTENSION_PUBLIC_ are inlined into the bundle as import.meta.env.*.

Try it locally

npx extension@latest create my-new-env --template new-env
cd my-new-env
npm install
npm run dev

A fresh browser window opens with the extension already loaded.

Project layout

src/
├── images/
│   └── icon.png
├── newtab/
│   ├── index.html
│   ├── scripts.ts
│   └── styles.css
├── background.js
└── manifest.json

Commands

Cloned this repo instead? The examples ship without npm scripts, so run Extension.js directly from the example directory. Run npm install first when the example declares dependencies.

dev

Run the extension in development mode. Target a browser with --browser:

npx extension@latest dev .                  # Chromium (default)
npx extension@latest dev . --browser=chrome
npx extension@latest dev . --browser=edge
npx extension@latest dev . --browser=firefox

build

Build for production:

npx extension@latest build .                # Chromium (default)
npx extension@latest build . --browser=firefox
npx extension@latest build . --browser=edge

preview

Preview the production build with the bundled browser:

npx extension@latest preview .

Tests

This template ships an end-to-end check (template.spec.ts) validated by the examples-repo CI on every commit.

Learn more

• Extension.js docs
• Templates index
• GitHub: extension-js/extension.js