Sidebar page

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JavaScript Sidebar Example

Adds a sidebar panel to the browser with a simple page.

What you'll see: A browser side panel that loads when you open the sidebar.

How it works: The manifest registers a side panel (chromium:side_panel / firefox:sidebar_action) that loads a JavaScript page bundled from src/sidebar/.

Try it locally

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

A fresh browser window opens with the extension already loaded.

Project layout

src/
├── images/
│   └── icon.png
├── sidebar/
│   ├── index.html
│   ├── scripts.js
│   └── 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