Content scripts

Injects a small badge into every web page you visit, with an options page that moves it to the left or right edge.

Runs on Chrome, Edge, Firefox · Manifest V3 · Surfaces: content script, options page, background service worker · Styling: CSS · Level: beginner

Create this project

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

What it is for

  • A plain JavaScript UI injected into every page
  • One position setting shared between an options page and a content script
  • Starting point for content scripts that need preferences

First steps

  • Run npm run dev to launch the extension
  • Click Open options on the badge injected into the page
  • Tick the setting and watch the badge move to the left edge

Permissions it asks for

  • storage
  • <all_urls>

Source on GitHubDocumentation

extension.devDocumentation for extension.dev