Scaffold extension with manifest.json and popup

~20 min

Set up the Chrome extension project structure with Manifest V3, a popup UI, and the basic file scaffolding.

Create a new project directory and open it in VS Code
Create the manifest.json file with Manifest V3 format - this is the extension's config file
Create popup.html and popup.js for the extension's popup UI
Create a styles.css for your popup styling
Load the extension in Chrome: go to chrome://extensions, enable Developer Mode, click "Load unpacked", and select your project folder

manifest.json

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0.0",
  "description": "A useful Chrome extension",
  "permissions": ["storage", "activeTab"],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icon-48.png"
  },
  "background": {
    "service_worker": "background.js"
  },
  "content_scripts": [{
    "matches": ["<all_urls>"],
    "js": ["content.js"]
  }],
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  }
}

popup.html

<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="styles.css">
</head>
<body>
  <div id="app">
    <h1>My Extension</h1>
    <div id="auth-section">
      <button id="login-btn">Sign In</button>
    </div>
    <div id="main-section" style="display:none">
      <p>Welcome! Extension is active.</p>
      <button id="action-btn">Do Something</button>
    </div>
  </div>
  <script src="popup.js"></script>
</body>
</html>

background.js

// Background service worker
chrome.runtime.onInstalled.addListener(() => {
  console.log('Extension installed')
})

// Listen for messages from popup or content scripts
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.type === 'GET_DATA') {
    // Handle data requests
    sendResponse({ status: 'ok' })
  }
  return true // Keep message channel open for async
})

💡

Tip: Keep chrome://extensions open in a pinned tab during development. Click the refresh icon on your extension after every change to reload it.

2

Build the core feature in content and background scripts

~40 min

Implement your extension's main functionality using content scripts for page interaction and the background service worker for logic.

Create content.js - this runs on every page the user visits and can read or modify the DOM
Use chrome.runtime.sendMessage() in the content script to communicate with the background worker
In background.js, handle messages and use chrome.storage.local to persist data between sessions
Build the popup UI logic in popup.js - query the active tab and display relevant data
Test thoroughly: load the extension, visit a page, open the popup, and verify all communication works

content.js

// Content script - runs on web pages
(function() {
  // Example: extract page data
  const pageData = {
    title: document.title,
    url: global.location.href,
    text: document.body.innerText.substring(0, 1000)
  }

  // Send data to background script
  chrome.runtime.sendMessage(
    { type: 'PAGE_DATA', data: pageData },
    (response) => console.log('Saved:', response)
  )
})()

💡

Tip: Use Chrome DevTools to debug your extension: right-click the popup → Inspect for popup debugging, and check the "Service Worker" link on chrome://extensions for background script logs.

⚠️

Warning: Content scripts run in an isolated world - they can access the DOM but not the page's JavaScript variables directly. Use global.postMessage if you need to communicate with page scripts.

3

Set up Supabase for user data and auth

~30 min

Add user authentication and cloud data storage so users can sync their extension data across devices.

Create a Supabase project at supabase.com and grab your project URL and anon key
Install the Supabase JS client by including it via CDN in your popup.html or bundling it
Implement Google OAuth login in your popup - Supabase handles the OAuth flow, you just need to open the auth URL
Create a user_data table in Supabase to store user-specific extension data
Enable Row Level Security so users can only access their own data

lib/supabase.js

import { createClient } from '@supabase/supabase-js'

const supabaseUrl = 'https://your-project.supabase.co'
const supabaseKey = 'your-anon-key'

export const supabase = createClient(supabaseUrl, supabaseKey)

export async function signInWithGoogle() {
  const { data, error } = await supabase.auth.signInWithOAuth({
    provider: 'google',
    options: {
      redirectTo: chrome.identity.getRedirectURL()
    }
  })
  return { data, error }
}

export async function saveUserData(userId, data) {
  return await supabase
    .from('user_data')
    .upsert({ user_id: userId, ...data })
}

💡

Tip: Use chrome.identity.getRedirectURL() for your OAuth redirect - Chrome provides a special URL for extension auth flows that avoids CORS issues.

⚠️

Warning: Never hardcode your Supabase service_role key in the extension. Only use the anon key - the extension code is readable by anyone who installs it.

4

Add Stripe for premium features

~30 min

Gate premium features behind a Stripe subscription and manage entitlements from your backend.

Create a Stripe account and set up a product with monthly and yearly price tiers
Build a checkout API route on your Vercel landing page that creates Stripe Checkout Sessions
From the extension popup, redirect free users to your Vercel-hosted pricing page when they try premium features
Set up a Stripe webhook on Vercel to update the user's subscription status in Supabase when they pay
In the extension, check the user's subscription status from Supabase before enabling premium features

popup.js (premium check)

async function checkPremiumStatus(userId) {
  const { data } = await supabase
    .from('subscriptions')
    .select('status, plan')
    .eq('user_id', userId)
    .single()

  if (data?.status === 'active') {
    // Enable premium features
    document.getElementById('premium-features').style.display = 'block'
    document.getElementById('upgrade-banner').style.display = 'none'
  } else {
    // Show upgrade prompt
    document.getElementById('upgrade-banner').style.display = 'block'
  }
}

💡

Tip: Offer a generous free tier. Extensions grow through word of mouth - free users who love your tool will upgrade when they hit the limit.

⚠️

Warning: Never process payments inside the extension popup. Always redirect to an external checkout page - Chrome Web Store policy prohibits in-extension payment processing.

5

Create landing page on Vercel and publish to Chrome Web Store

~30 min

Build a landing page for your extension, push your code to GitHub, and submit to the Chrome Web Store.

Create a Next.js or static landing page with: hero section, feature list, pricing, and a "Add to Chrome" CTA button
Deploy the landing page to Vercel by connecting your GitHub repo
Add your Stripe webhook endpoint and checkout API routes to the Vercel project
Package your extension: zip the extension folder (excluding node_modules and .git)
Go to the Chrome Web Store Developer Dashboard, pay the $5 registration fee, upload your zip, add screenshots and descriptions, and submit for review

Terminal

# Package extension for Chrome Web Store
cd my-extension
zip -r ../my-extension.zip . -x "node_modules/*" ".git/*" "*.map"

💡

Tip: Chrome Web Store review takes 1-3 business days. Have your landing page live and your Stripe integration tested before submitting so you can start selling immediately on approval.

⚠️

Warning: Read the Chrome Web Store developer policies carefully. Extensions that request unnecessary permissions or have unclear privacy policies get rejected.

Build a Chrome Extension

What You'll Build

Prerequisites

Architecture

5 Steps

Scaffold extension with manifest.json and popup

Build the core feature in content and background scripts

Set up Supabase for user data and auth

Add Stripe for premium features

Create landing page on Vercel and publish to Chrome Web Store

🎉 You're Done!

Want this built for you?

Build a Chrome Extension

What You'll Build

Prerequisites

Architecture

5 Steps

Scaffold extension with manifest.json and popup

Build the core feature in content and background scripts

Set up Supabase for user data and auth

Add Stripe for premium features

Create landing page on Vercel and publish to Chrome Web Store

🎉 You're Done!

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