Shows a small overlay UI on every web page, with an options page that moves it from right to left.
npx extension@latest create my-content-typescript --template content-typescript
cd my-content-typescript
npm install
npm run dev!Powered by Extension.js
Shows a small overlay UI on every web page, with an options page that moves it from right to left.
What you'll see: A small UI injected into any web page, isolated in a Shadow DOM so site styles don't bleed through. The overlay carries an Open options button, and the options page behind it has one checkbox that moves the overlay between the right and left edge of the page, live.
How it works: A content script mounts a TypeScript UI inside a Shadow DOM and applies scoped styles so the host page can't bleed through.
The template ships two more surfaces on top of that overlay. The manifest registers an options_ui page bundled from src/options/, which reads the badgePosition setting with chrome.storage.sync.get on load and writes it back with chrome.storage.sync.set on change. The value is right by default and left when the box is ticked. The content script reads the same key on injection and subscribes to chrome.storage.onChanged, so ticking the box slides the overlay to the other edge on every open page without a reload. The subscription is removed in the cleanup function the framework calls, next to the overlay teardown.
A content script cannot open the options page itself, because chrome.runtime.openOptionsPage lives on the extension side. The Open options button sends {type: 'open-options'} to the background script, and the background script opens the page. Both ends import the message and settings types from src/types.ts, so the two surfaces cannot drift apart without a type error.
npx extension@latest create my-content-typescript --template content-typescript
cd my-content-typescript
npm install
npm run devA fresh browser window opens with the extension already loaded.
src/
├── content/
│ ├── scripts.ts
│ └── styles.css
├── images/
│ └── icon.png
├── options/
│ ├── index.html
│ ├── scripts.ts
│ └── styles.css
├── background.ts
├── types.ts
└── manifest.jsonCloned 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.
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=firefoxBuild for production:
npx extension@latest build . # Chromium (default)
npx extension@latest build . --browser=firefox
npx extension@latest build . --browser=edgePreview the production build with the bundled browser:
npx extension@latest preview .This template ships an end-to-end check (template.spec.ts) validated by the examples-repo CI on every commit.