DEV Community

Cover image for How to build your next Chrome extension with Svelte
Mauro Garcia
Mauro Garcia

Posted on • Originally published at

How to build your next Chrome extension with Svelte

I've been working on a side project called Research Pal. It's a simple yet useful Chrome extension that lets you track and manage your researches.
After following the basic tutorials available in the Chrome Developers Portal, I learned that you just need HTML, CSS, and JavaScript to build an extension.

But the problem is that Research Pal will have a couple of different "screens" or "sections" that will be shown based on different conditions. Besides, the user will be able to navigate between "screens" through interactions. I don't know you, but I don't want to handle all that state logic with plain JavaScript πŸ˜†

Presenting Svelte

If it's the first time you hear about Svelte, I strongly recommend you to take a look at the official website.

You can also check out some of my previous post about svelte:

One of the things that set Svelte apart from other JS frameworks is that instead of doing the bulk of their work in the browser, it shifts that work into a compile step that happens when you build your app.

I could speak about Svelte for hours, but let's see how we can use it for our Chrome extensions.

1. Create your Svelte app

We need to use degit to create our Svelte app. Run the following commands:

npx degit sveltejs/template my-svelte-project
cd my-svelte-project
npm install
npm run dev
Enter fullscreen mode Exit fullscreen mode

If everything went as expected, you should be able to see your app running on http://localhost:3000.

2. Add your Chrome extension

For this tutorial, we'll need to create a folder called "extension". Then, create the following files inside our new folder:


  "name": "Counter App",
  "version": "1.0",
  "description": "Chrome extension + Svelte boilerplate",
  "permissions": ["activeTab"],
  "browser_action": {
    "default_popup": "popup.html",
  "manifest_version": 2
Enter fullscreen mode Exit fullscreen mode


<!DOCTYPE html>
<html lang="en">
    <meta charset='utf-8'>
    <meta name='viewport' content='width=device-width,initial-scale=1'>

    <title>Counter App</title>

    <!-- CSS Bundle generated by Svelte -->
    <link rel='stylesheet' href='/build/bundle.css'>

    <!-- JS Bundle generated by Svelte -->
    <script defer src='/build/bundle.js'></script>

Enter fullscreen mode Exit fullscreen mode

If you want to dig into Chrome extension development, please take a look at @paulasantamaria 's post:

3. Add logic to your Svelte App

Go to your App.svelte and replace its content with the following code:

    let count = 0;

    function sum() {

<p>Counter: {count}</p>
<button on:click={sum}> + </button>

Enter fullscreen mode Exit fullscreen mode

4. Build your extension

When you run the npm run build script on a Svelte project, a new folder called public will appear.

Because we want to include our extension files within this folder with the Svelte files, we'll need to install a library called cpx:

npm install --save cpx
Enter fullscreen mode Exit fullscreen mode

Cpx will allow us to move files from our extension folder to our public folder on each build.

Finally, we need to update our build script within the package.json file like this:

  "scripts": {
-    "build": "rollup -c",   
+    "build": "cpx -C public/** public/** && rollup -c && cpx extension/**/*.* public",
Enter fullscreen mode Exit fullscreen mode

With this new script, we're deleting the public folder, building our Svelte app, and finally copying our extension files using cpx.

That's it. Now, you can go to Google Chrome and load your extension by following these steps:

  1. Go to chrome://extensions
  2. Click on the "Load unpacked" button
  3. Select your project's public folder

Every time you want to test an update, just run the build script and your extension will be reloaded in your browser.

Example of a chrome extension that uses Svelte

Show me the boilerplate!

Check out my github repo to get the boilerplate:

GitHub logo mauro-codes / chrome-extension-with-svelte

Boilerplate that includes a basic chrome extension that uses Svelte

Building your chrome extension

Run the following commands:

npm i
npm run build
Enter fullscreen mode Exit fullscreen mode

Your extension build will be available within the public folder.

If you want to know more about this boilerplate, check out my blog post

Let me know what you think in the comments below πŸ‘‡

Top comments (0)