How Does A Chrome Extension Work? (Web Development)

There are 5 parts to a Chrome extension:

1. the manifest file
2. the background script
3. the foreground script
4. the popup page
5. the options page

Everything begins with the manifest file…

// manifest.json{
"name": "obj ext",
"description": "my ext",
"version": "0.1.0",
"manifest_version": 2,
"icons": {
"16": "./obj-16x16.png",
"32": "./obj-32x32.png",
"48": "./obj-48x48.png",
"128": "./obj-128x128.png"
"background": {
"scripts": ["./background.js"]
"options_page": "./options.html",
"browser_action": {
"default_popup": "popup.html"
"permissions": [

The background script (background.js) is a JavaScript script that runs once our extension either gets installed or the user refreshes the extension manually.


We can make the Google homepage’s logo spin if we wanted to.

From there, our foreground.js script acts like any other script influencing an index.html page.

The popup page is optional.
The popup page is what shows when the user clicks on our extension icon in the top right.

The options page is just like the popup page.
It’s what the user sees when they navigate to their extensions tab and click for the options.

Chrome Extension Manifest Version 3 is out now!

How To Build A Chrome Extension (2020 Web Development)




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