extension-apis

# Chrome Extension APIs Reference

## chrome.runtime

### Lifecycle Events

```javascript
// Extension installed or updated
chrome.runtime.onInstalled.addListener((details) => {
  if (details.reason === 'install') {
    // First install
  } else if (details.reason === 'update') {
    // Updated from details.previousVersion
  }
});

// Browser started with extension enabled
chrome.runtime.onStartup.addListener(() => {
  // Browser startup
});

// Extension suspended (MV3)
chrome.runtime.onSuspend.addListener(() => {
  // Clean up before suspension
});
```

### Messaging

```javascript
// Send message to background
const response = await chrome.runtime.sendMessage({
  type: 'ACTION',
  data: payload
});

// Listen for messages
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  console.log('From:', sender.tab?.id || 'extension');

  // Async response - MUST return true
  handleAsync(message).then(sendResponse);
  return true;
});

// Connect for long-lived connection
const port = chrome.runtime.connect({ name: 'channel' });
port.postMessage({ type: 'HELLO' });
port.onMessage.addListener((message) => {
  console.log('Received:', message);
});
port.onDisconnect.addListener(() => {
  console.log('Port disconnected');
});
```

### Extension Info

```javascript
// Get extension info
const manifest = chrome.runtime.getManifest();
const id = chrome.runtime.id;
const url = chrome.runtime.getURL('page.html');

// Reload extension
chrome.runtime.reload();

// Open options page
chrome.runtime.openOptionsPage();
```

---

## chrome.storage

### Storage Areas

```javascript
// Local storage (10MB limit, persistent)
await chrome.storage.local.set({ key: 'value' });
const { key } = await chrome.storage.local.get('key');
const all = await chrome.storage.local.get(null);
await chrome.storage.local.remove('key');
await chrome.storage.local.clear();

// Sync storage (100KB limit, synced across devices)
await chrome.storage.sync.set({ settings: { theme: 'dark' } }