How to write a Google Chrome Extension

Google Chrome is one of the most popular web browsers in the world, and for good reason. It is fast, stable, and has a ton of features that make it a great choice for users of all levels. One of the best things about Chrome is the ability to extend its functionality through the use of extensions.

In this blog post, we will go over the basics of how to write a Google Chrome extension. Whether you are a beginner or an experienced developer, this tutorial will provide you with the knowledge you need to get started.

What is a Chrome Extension?

A Chrome extension is a small piece of software that extends the functionality of the Chrome browser. It can do things like modify the appearance of a web page, add new features to the browser, or even block ads.

There are thousands of extensions available in the Chrome Web Store, and they are a great way to customize your browsing experience.

Getting Started

Before we dive into the details of how to write a Chrome extension, let’s go over the tools you will need.

First and foremost, you will need a text editor. There are many options available, but some popular ones include Sublime Text, Visual Studio Code, and Atom.

In addition to a text editor, you will also need a basic understanding of HTML, CSS, and JavaScript. These are the languages that are used to build Chrome extensions, so it is important to have at least a basic understanding of them.

Finally, you will need to download and install the latest version of Google Chrome.

Creating the Extension

The first step in creating a Chrome extension is to create a new folder on your computer and name it whatever you want. This folder will contain all of the files for your extension.

Next, create a file inside the folder called manifest.json. This file is the heart of any Chrome extension, as it tells the browser what the extension does and how it should behave.

Here is a basic example of a manifest.json file:

“manifest_version”: 2,
“name”: “My Extension”,
“description”: “This is my first extension.”,
“version”: “1.0”,
“browser_action”: {
“default_icon”: “icon.png”,
“default_popup”: “popup.html”
“permissions”: [

Let’s go over each of the fields in this file:

manifest_version: This should always be set to 2.
name: The name of your extension.
description: A brief description of what your extension does.
version: The version number of your extension.
browser_action: This field tells Chrome what to do when the user clicks on the extension’s icon in the toolbar. In this example, the default icon is set to “icon.png” and the default popup is set to “popup.html”.
permissions: This field lists the permissions that your extension needs in order to function. In this example, the extension needs access to the active tab.
Next, create an “icon.png” file and a “popup.html” file in the extension folder. The “icon.png” file is the icon that will be displayed in the toolbar, and the “popup.html” file is the HTML code for the popup that appears when the user clicks on the extension’s icon.

Now that we have our manifest file and our icon and popup files set up, let’s move on to the actual functionality of the extension.

To do this, we will need to use JavaScript. Create a new file in the extension folder called “script.js” and include it in the “popup.html” file like this:

My Extension

Hello World!

Now we can use JavaScript to add functionality to the extension. For example, we can use the chrome.tabs API to interact with the current tab:

chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {

This code will log the URL of the current tab to the console.

There are many other APIs available for interacting with the browser and web pages, such as for storing data, chrome.history for interacting with the browsing history, and chrome.alarms for scheduling tasks.

Installing the Extension

Now that we have our extension built, it’s time to install it in Chrome.

To do this, open Chrome and go to the extensions page by clicking on the three dots in the top right corner, then going to “More tools” and selecting “Extensions”.

On the extensions page, click on the “Load unpacked” button and select the folder that contains your extension files.

The extension should now be installed and visible in the toolbar. Click on the icon to see the popup in action.


Writing a Google Chrome extension is a great way to add custom functionality to the browser and make your web browsing experience more personalized. With just a few lines of code, you can create something that can improve your productivity, block distracting ads, or even add a fun Easter egg to your favorite websites.

I hope this tutorial has given you a good understanding of the basics of creating a Chrome extension. Happy coding!

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