How to Build a Chrome Extension with Manifest V3 — Complete Guide

Chrome extensions are one of the easiest ways to build a product that reaches millions of users. And with Manifest V3, Google has made the platform more secure and performant. Here's everything you need to know to build your first Chrome extension. Project Structure A Chrome extension has 4 main parts: my-extension/ ├── manifest.json # Config file (the brain) ├── background/ │ └── background.js # Runs in background (API calls, events) ├── content/ │ ├── content.js # Injected into web pages │ └── content.css # Styles for injected UI ├── popup/ │ ├── popup.html # Click extension icon → this opens │ ├── popup.css │ └── popup.js └── icons/ ├── icon16.png ├── icon48.png └── icon128.png Step 1: manifest.json This is the config file that tells Chrome what your extension does: { "manifest_version" : 3 , "name" : "My Extension" , "version" : "1.0.0" , "description" : "What your extension does" , "permissions" : [ "storage" , "activeTab" ], "action" : { "default_popup" : "popup/popup.html" , "de