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The Bitwarden browser extension is a cross-platform password manager built using the Web Extension API and Angular. It provides secure password management, autofill capabilities, and vault access directly from the browser.

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Supported Browsers

The extension supports all major browsers:
  • Chrome - Chrome Web Store
  • Firefox - Firefox Add-ons
  • Safari - App Store (macOS)
  • Edge - Microsoft Edge Add-ons
  • Opera - Opera Add-ons
  • Vivaldi - Chrome Web Store compatible
  • Brave - Chrome Web Store compatible

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Manifest V3

The browser extension uses Web Extension API Manifest V3, the latest extension platform standard. Manifest V3 brings significant architectural changes:

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Key Changes from Manifest V2

  • Service Workers replace persistent background pages
  • Background context can be terminated at any time by the browser
  • Enhanced security and privacy controls
  • Improved extension performance
See Manifest V3 Migration for detailed information about the differences and migration.

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Architecture

The extension is organized into distinct execution contexts:

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Execution Contexts

  • Background Service Worker (src/platform/background.ts) - Handles core business logic, API calls, and vault operations
  • Popup (src/popup/) - The main UI shown when clicking the extension icon
  • Content Scripts (src/autofill/) - Injected into web pages for autofill and form detection
  • Offscreen Documents - Used for clipboard operations in Manifest V3

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Cross-Browser Compatibility

The codebase uses the BrowserApi abstraction layer (src/platform/browser/browser-api.ts) to handle browser-specific differences: 
// Never use chrome.* or browser.* APIs directly
// ❌ Bad
chrome.tabs.query({ active: true }, callback);

// ✅ Good - Use BrowserApi abstraction
await BrowserApi.tabsQuery({ active: true });
This abstraction ensures compatibility across Chrome, Firefox, Safari, Opera, and other Chromium-based browsers.

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Source Code Structure

apps/browser/
├── src/
│   ├── autofill/           # Autofill and form detection
│   ├── background/         # Background service worker logic
│   ├── platform/           # Platform-specific services
│   │   └── browser/        # BrowserApi abstraction
│   ├── popup/              # Extension popup UI
│   ├── vault/              # Vault management
│   ├── manifest.json       # Manifest V2 (legacy)
│   └── manifest.v3.json    # Manifest V3 (current)
├── package.json            # Build scripts and dependencies
└── webpack.config.js       # Build configuration

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Browser-Specific Features

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Safari

Safari has unique requirements and limitations:
  • Requires manual event listener cleanup to prevent memory leaks
  • Tab query APIs can return unexpected results across windows
  • Native messaging for clipboard operations
See the Architecture page for Safari-specific patterns.

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Firefox

Firefox supports both Manifest V2 and V3:
  • Uses browser.* API namespace (Web Extensions API)
  • Sidebar action support
  • Android support for Firefox Mobile

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Build Targets

The extension can be built for different browsers and manifest versions: 
# Chrome (Manifest V3)
npm run build:chrome

# Firefox (Manifest V2 by default)
npm run build:firefox

# Firefox (Manifest V3)
cross-env MANIFEST_VERSION=3 npm run build:firefox

# Safari
npm run build:safari

# Edge
npm run build:edge

# Opera
npm run build:opera
See Building for complete build instructions.

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Development Mode

For active development with automatic rebuilding: 
# Watch mode for Chrome
npm run build:watch:chrome

# Watch mode for Firefox
npm run build:watch:firefox

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Next Steps

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