Have you ever wanted to customize or enhance your browsing experience? Perhaps block annoying ads, integrate tools you frequently use, or automate repetitive tasks?
If so, learning how to build Chrome extensions is a great skill to have.
Chrome extensions are bits of code that extend the functionality of Google‘s popular Chrome browser. They allow you to tweak and personalize your browsing in ways that plain vanilla Chrome just doesn‘t offer out of the box.
The best part is, you don‘t need to be an expert coder to build browser extensions. With just basic web dev skills, you can put together a simple yet functional Chrome extension in no time.
Let‘s walk through the process step-by-step. By the end, you‘ll have created your first Chrome extension!
Why Create a Chrome Extension?
Before we dive in, let‘s briefly go over why you may want to build a Chrome extension in the first place:
Customize the browsing experience – Change the appearance and behavior of Chrome to suit your preferences
Automate repetitive tasks – Streamline workflows by setting up shortcuts and triggers
Integrate tools/services – Incorporate external resources seamlessly into your browser
Developer convenience – Useful for testing sites, debugging code and more
Privacy/security – Block unwanted content, limit tracking and secure your data
Share useful functionality – Solve pain points for other users and publish your work
The possibilities are endless. People have built Chrome extensions for everything from to-do list managers and coupon finders to RSS feed readers and collaboration tools.
If you have an idea that could potentially enhance how you (or others) interact with the web, building a Chrome extension is the way to bring that concept to life.
Curious to learn how? Let‘s get cracking!
Step 1 – Set Up the Manifest File
The manifest file is the only file absolutely necessary for developing a Chrome extension. Seen as a configuration file, it tells Chrome about your extension‘s capabilities, resources, and overall structure.
Here‘s a boilerplate manifest to get us started:
{
"manifest_version": 3,
"name": "My First Extension",
"version": "1.0",
"description": "My awesome Chrome extension!",
"action": {
"default_popup": "popup.html"
}
}Breaking this down bit by bit:
- manifest_version: Required – currently must be set to 3
- name: Required – extension‘s display name users will see
- version: Optional – extension‘s version number
- description: Optional – short blurb explaining what your extension does
- action: Optional – defines extension‘s UI components; we‘re using a popup window
The manifest above configures our extension to show a popup named "popup.html" when clicked. Popup windows are one of the simplest UI options.
Later, we can beef up the manifest with other properties like icons, permissions, content scripts and more. But this will work for now.
Save the file as manifest.json at the root of your project directory.
Step 2 – Add the Popup File
As mentioned, we‘ll be using a popup window for basic UI. The default_popup property tells Chrome to open the defined HTML file when our extension icon is clicked.
Create a file named popup.html and add the following:
<!DOCTYPE html>
<html>
<head>
<title>My Test Extension</title>
</head>
<body>
<p>Welcome to my Chrome extension popup.</p>
<script src="popup.js"></script>
</body>
</html>Fairly barebones but it gets the job done.
We have a heading, paragraph for content and include popup.js which we‘ll create next. Nothing fancy required.
Step 3 – Add JavaScript Functionality
No extension would be complete without some custom JavaScript to handle the logic. We‘ll add a tiny bit of JS to show a simple alert message when the popup loads.
Create a file named popup.js:
window.onload = function() {
alert("Hello from popup.js!");
}This triggers a popup alert using the common window.onload event handler.
And that concludes the 3 absolutely essential components of a basic Chrome extension:
- Manifest – Configuration
- HTML – Structure
- JS – Functionality
With just those pieces, you can already build tons of helpful extensions. But let‘s keep going to really cement these concepts.
Step 4 – Load the Extension in Chrome
We‘re now ready to see our extension in action. Time to load it up in the browser!
- Open Chrome and type
chrome://extensionsin the address bar - Turn on "Developer Mode" via the toggle in the top right
- Click "Load Unpacked"
- Select the folder containing your extension‘s manifest and other files
That installs the extension locally. You should now see the popup trigger when clicking your extension icon next to the address bar.
Give it try! Our alert from popup.js should display confirming everything is wired up properly.
With the extension loaded, feel free to tweak the code and reload to test changes. The updates should apply instantly without needing to reinstall each time.
Step 5 – Use Chrome APIs
So our extension works as intended. But it‘s not terribly exciting yet. Let‘s spice things up by integrating the browser‘s native APIs.
Chrome offers a wealth of APIs allowing extensions to do things like:
- Read/modify tabs
- Interact with history & bookmarks
- Make cross-domain XMLHTTPRequests
- Store/retrieve data locally
- Communicate across scripts
And more. We have the full power of Chrome at our fingertips!
Let‘s demonstrate by pulling up the user‘s browsing history and showing the last 10 sites visited:
// popup.js
let ul = document.getElementById("historyList");
chrome.history.search({text: ‘‘, maxResults: 10}, function(data) {
data.forEach(function(page) {
let li = document.createElement(‘li‘);
li.innerHTML = page.title + " (" + page.url + ")";
ul.appendChild(li);
})
});Here we:
- Use
chrome.historyAPI to search visit history - Loop through the results
- Append each entry to the page as list items
Then in popup.html:
<ul id="historyList"></ul>Gives the output an unordered list to populate.
Load this updated version in Chrome and…voila! You should now have a list of recent pages you‘ve visited:
Pretty slick for only using the basic Chrome APIs! Just imagine what‘s possible by mixing and matching other browser features.
Step 6 – Publish the Extension
Once you‘ve built something useful, you can optionally publish your extension publicly to the Chrome Web Store. This allows other Chrome users to discover and install your creation.
The main steps are:
1. Refine details in manifest – Add icon images, update description, handling updates, etc.
2. Sign up as a Chrome Developer – Free one-time registration to access Web Store dashboard
3. Zip extension folder into .crx package – Required upload format
4. Submit to Chrome Web Store – Upload .crx and images via dashboard
5. Test & launch extension – Preview before going live to all users
I won‘t cover the entire publishing process here but just know it‘s definitely achievable for independent devs. Googlecharges a small $5 registration fee to deter spam/abuse.
If releasing your extension publicly doesn‘t interest you, no worries! Extensions you load unpacked like we did are still perfectly usable in your local Chrome instance.
Wrap Up & Next Steps
And with that, you‘ve successfully built your first Chrome extension from scratch!
We covered:
- The core components of an extension
- Working with the manifest, HTML and JS
- Loading extensions locally for testing
- Using powerful Chrome APIs for added functionality
- Publishing to the world (optional)
Of course there‘s a near endless amount you can still do when building browser extensions. This guide just scratches the surface.
Some ideas for taking your skills further:
- Explore more advanced APIs in depth
- Build options pages for managing configurations
- Implement content scripts for analyzing web pages
- Handle background scripts for event handling
- Learn tricks to debung extensions efficiently
- Read the handy Chrome Extension API Reference docs
Feel free to use what you‘ve learned here as a springboard for building more advanced functionality.
The Chrome extension ecosystem offers a massive playground to let your creativity run wild! Implement that clever idea you‘ve been pondering to streamline web workflows or make browsing life easier.
Happy coding!
