Chrome Extension Development with WXT

Chrome Extension Development with WXT

Build modern, cross-browser extensions using WXT - the next-generation framework that supports Chrome, Firefox, Edge, Safari, and all Chromium browsers with a single codebase.

When to Use This Skill

Use this skill when:

• Creating a new Chrome/​browser extension
• Setting up WXT development environment
• Building extension features (popup, content scripts, background scripts)
• Implementing cross-browser compatibility
• Working with Manifest V3 (mandatory standard as of 2025, V2 deprecated)
• Integrating React 19, Vue, Svelte, or Solid with extensions

Quick Start Workflow

1. Initialize WXT Project

# Create new project with framework of choice
npm create wxt@latest

# Or with specific template
npm create wxt@latest -- --template react-ts
npm create wxt@latest -- --template vue-ts
npm create wxt@latest -- --template svelte-ts

2. Project Structure

WXT uses file-based conventions:

project/
├── entrypoints/              # Auto-discovered entry points
│   ├── background.ts         # Service worker
│   ├── content.ts           # Content script
│   ├── popup.html           # Popup UI
│   └── options.html         # Options page
├── components/              # Auto-imported UI components
├── utils/                   # Auto-imported utilities
├── public/                  # Static assets
│   └── icon/               # Extension icons
├── wxt.config.ts           # Configuration
└── package.json

3. Development Commands

npm run dev              # Start dev server with HMR
npm run build           # Production build
npm run zip             # Package for store submission

Core Entry Points

WXT recognizes entry points by filename in entrypoints/ directory:

Background Script (Service Worker)

// entrypoints/​background.ts
export default defineBackground({
  type: 'module',
  persistent: false,

  main() {
    // Listen for extension events
    browser.action.onClicked.addListener((tab) => {
      console.log('Extension clicked', tab);
    });

    // Handle messages
    browser.runtime.onMessage.addListener((message, sender, sendResponse) => {
      // Handle message
      sendResponse({ success: true });
      return true; // Keep channel open for async
    });
  },
});

Content Script

// entrypoints/​content.ts
export default defineContentScript({
  matches: ['*://*.example.com/​*'],
  runAt: 'document_end',

  main(ctx) {
    // Content script logic
    console.log('Content script loaded');

    // Create UI
    const ui = createShadowRootUi(ctx, {
      name: 'my-extension-ui',
      position: 'inline',
      anchor: 'body',

      onMount(container) {
        // Mount React/​Vue component
        const root = ReactDOM.createRoot(container);
        root.render(<App />);
      },
    });

    ui.mount();
  },
});

Popup UI

// entrypoints/​popup/​main.tsx
import React from 'react';
import ReactDOM from 'react-dom/​client';
import App from './​App';

ReactDOM.createRoot(document.getElementById('root')!).render(
  <React.StrictMode>
    <App />
  </​React.StrictMode>
);

<!-- entrypoints/​popup/​index.html -->
<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Extension Popup</​title>
</​head>
<body>
  <div id="root"></​div>
  <script type="module" src="./​main.tsx"></​script>
</​body>
</​html>

Configuration

Basic wxt.config.ts

import { defineConfig } from 'wxt';

export default defineConfig({
  // Framework integration
  modules: ['@wxt-dev/​module-react'],

  // Manifest configuration
  manifest: {
    name: 'My Extension',
    description: 'Extension description',
    permissions: ['storage', 'activeTab'],
    host_permissions: ['*://example.com/​*'],
  },

  // Browser target
  browser: 'chrome', // or 'firefox', 'edge', 'safari'
});

Common Patterns

Type-Safe Storage

// utils/​storage.ts
import { storage } from 'wxt/​storage';

export const storageHelper = {
  async get<T>(key: string): Promise<T | null> {
    return await storage.getItem<T>(`local:${key}`);
  },

  async set<T>(key: string, value: T): Promise<void> {
    await storage.setItem(`local:${key}`, value);
  },

  watch<T>(key: string, callback: (newValue: T | null) => void) {
    return storage.watch<T>(`local:${key}`, callback);
  },
};

Type-Safe Messaging

// utils/​messaging.ts
interface Messages {
  'get-data': {
    request: { key: string };
    response: { value: any };
  };
}

export async function sendMessage<K extends keyof Messages>(
  type: K,
  payload: Messages[K]['request']
): Promise<Messages[K]['response']> {
  return await browser.runtime.sendMessage({ type, payload });
}

Script Injection

// Inject script into page context
import { injectScript } from 'wxt/​client';

await injectScript('/​injected.js', {
  keepInDom: false,
});

Building & Deployment

Production Build

# Build for specific browser
npm run build -- --browser=chrome
npm run build -- --browser=firefox

# Create store-ready ZIP
npm run zip
npm run zip -- --browser=firefox

Multi-Browser Build

# Build for all browsers
npm run zip:all

Output: .output/​my-extension-{version}-{browser}.zip

Modern Stacks (2025)

Popular technology combinations for building Chrome extensions:

WXT + React + Tailwind + shadcn/​ui

Most popular stack in 2025. Combines utility-first styling with pre-built accessible components.

npm create wxt@latest -- --template react-ts
npm install -D tailwindcss postcss autoprefixer
npx tailwindcss init -p
npx shadcn@latest init

Best for: Modern UIs with consistent design system Example: https://github.com/imtiger/wxt-react-shadcn-tailwindcss-chrome-extension

WXT + React + Mantine UI

Complete component library with 100+ components and built-in dark mode.

npm create wxt@latest -- --template react-ts
npm install @mantine/​core @mantine/​hooks

Best for: Feature-rich extensions needing complex components Example: https://github.com/ongkay/WXT-Mantine-Tailwind-Browser-Extension

WXT + React + TypeScript (Minimal)

Clean setup for custom designs without UI library dependencies.

npm create wxt@latest -- --template react-ts

Best for: Simple extensions or highly custom designs

Advanced Topics

For detailed information on advanced topics, see the reference files:

• React Integration: See references/​react-integration.md for complete React setup, hooks, state management, and popular UI libraries
• Chrome APIs: See references/​chrome-api.md for comprehensive Chrome Extension API reference with examples
• Chrome 140+ Features: See references/​chrome-140-features.md for latest Chrome Extension APIs (sidePanel.getLayout(), etc.)
• WXT API: See references/​wxt-api.md for complete WXT framework API documentation
• Best Practices: See references/​best-practices.md for security, performance, and architecture patterns

Troubleshooting

Common issues and solutions:

1. Module not found errors: Ensure modules are installed and properly imported
2. CSP violations: Update content_security_policy in manifest
3. Hot reload not working: Check browser console for errors
4. Storage not persisting: Use storage.local or storage.sync correctly

For detailed troubleshooting, see references/​troubleshooting.md

Resources

Official Documentation

• WXT Docs: https://wxt.dev
• Chrome Extension Docs: https://developer.chrome.com/docs/extensions
• Firefox Extension Docs: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons

Bundled Resources

• scripts/​: Helper utilities for common extension tasks
• references/​: Detailed documentation for advanced features
• assets/​: Starter templates and example components

Use these resources as needed when building your extension.