name: chrome-extension description: Build Chrome Extensions with Manifest V3, background service workers, content scripts, and message passing. Use when developing TikTok Uploader extension or any browser extensions.

🔌 Chrome Extension Skill

Use Cases

• TikTok auto-uploader
• Web automation tools
• Content modification
• Data extraction

Manifest V3 Structure

{
  "manifest_version": 3,
  "name": "Extension Name",
  "version": "1.0.0",
  "permissions": ["activeTab", "storage", "tabs"],
  "host_permissions": ["https://*.tiktok.com/*"],
  "background": {
    "service_worker": "background.js"
  },
  "content_scripts": [{
    "matches": ["https://*.tiktok.com/*"],
    "js": ["content.js"]
  }],
  "action": {
    "default_popup": "popup.html"
  },
  "side_panel": {
    "default_path": "sidepanel.html"
  }
}

Message Passing

Content → Background

// content.js
chrome.runtime.sendMessage({ type: 'UPLOAD_COMPLETE', data: result });

// background.js
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.type === 'UPLOAD_COMPLETE') {
    console.log('Upload done:', message.data);
    sendResponse({ success: true });
  }
  return true; // Keep channel open for async
});

Background → Content

// background.js
chrome.tabs.sendMessage(tabId, { type: 'START_UPLOAD', file: fileData });

// content.js
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.type === 'START_UPLOAD') {
    handleUpload(message.file);
  }
});

Storage Patterns

Local Storage

// Save
await chrome.storage.local.set({ uploadQueue: files });

// Load
const { uploadQueue } = await chrome.storage.local.get('uploadQueue');

// Listen for changes
chrome.storage.onChanged.addListener((changes, area) => {
  if (area === 'local' && changes.uploadQueue) {
    console.log('Queue updated:', changes.uploadQueue.newValue);
  }
});

Side Panel

Enable in manifest

"side_panel": {
  "default_path": "sidepanel.html"
}

Open programmatically

chrome.sidePanel.open({ windowId: window.id });

Trusted Types (CSP Fix)

// Create policy
const trustedPolicy = trustedTypes.createPolicy('my-policy', {
  createHTML: (input) => input
});

// Use for innerHTML
element.innerHTML = trustedPolicy.createHTML(htmlString);

Service Worker Persistence

// Keep alive with alarm
chrome.alarms.create('keepAlive', { periodInMinutes: 1 });

chrome.alarms.onAlarm.addListener((alarm) => {
  if (alarm.name === 'keepAlive') {
    // Do minimal work to stay alive
  }
});

Decision Tree

Extension task?
├── Background work? → Service Worker
├── Page modification? → Content Script
├── User UI? → Popup or Side Panel
├── Cross-script data? → Message passing
└── Persist data? → chrome.storage

TikTok Uploader Patterns

1. Round-Robin Folders

async function getNextFile() {
  const { folders, lastIndex } = await chrome.storage.local.get();
  const nextIndex = (lastIndex + 1) % folders.length;
  const folder = folders[nextIndex];
  
  const files = await fetchFilesFromFolder(folder);
  await chrome.storage.local.set({ lastIndex: nextIndex });
  
  return files[0];
}

2. Upload Queue Management

// Add to queue
await addToQueue(file);

// Process queue
async function processQueue() {
  const { queue } = await chrome.storage.local.get('queue');
  if (queue.length > 0) {
    const file = queue.shift();
    await uploadFile(file);
    await chrome.storage.local.set({ queue });
    processQueue(); // Continue
  }
}

Common Issues