Build Your First Chrome Extension With Rust and WebAssembly

This article will help you transform your browser extension development by combining Rust's safety with WebAssembly's performance.

Jan. 16, 25 · Tutorial

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Chrome extensions have traditionally been built using JavaScript, HTML, and CSS. However, with the rise of WebAssembly (Wasm), we can now leverage Rust's performance, safety, and modern development features in browser extensions.

In this tutorial, we will create a simple Chrome extension that uses Rust compiled to WebAssembly.

Prerequisites

Before we begin, you'll need:

    Plain Text
   
   # Install Rust and Cargo
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Install Node.js and npm (using nvm for version management)
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash && nvm install 23

# Install wasm-pack (required for WebAssembly compilation and JavaScript bindings)
cargo install wasm-pack

Note: While Rust and Cargo provide basic WebAssembly support, we specifically need wasm-pack for this project as it handles the WebAssembly compilation process and generates optimized JavaScript bindings for browser integration.

Project Structure

Our Chrome extension will have the following structure:

    Plain Text
   
 

   rust-chrome-extension/
├── Cargo.toml
├── manifest.json
├── package.json
├── popup.html
├── popup.js
└── src/
    └── lib.rs
  

Setting Up the Project

1. First, create a new Rust project:

    Plain Text
   
   cargo new rust-chrome-extension --lib
cd rust-chrome-extension

2. Update your Cargo.toml with the necessary dependencies:

    Plain Text
   
 

   [package]
name = "rust-chrome-extension"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["cdylib"]

[dependencies]
wasm-bindgen = "0.2"
  

3. Create a simple Rust function in src/lib.rs:

    Plain Text
   
   use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn greet(name: &str) -> String {
    format!("Hello, {}! From Rust!", name)
}

4. Create manifest.json for the Chrome extension:

    Plain Text
   
 

   {
  "manifest_version": 3,
  "name": "Rust Chrome Extension",
  "version": "1.0",
  "description": "A simple Chrome extension using Rust and WebAssembly",
  "action": {
    "default_popup": "popup.html"
  }
}
  

5. Create popup.html:

    Plain Text
   
 

   <!DOCTYPE html>
<html>
<head>
  <title>Rust Chrome Extension</title>
</head>
<body>
  <input type="text" id="name" placeholder="Enter your name">
  <button id="greet">Greet</button>
  <div id="output"></div>
  <script src="pkg/rust_chrome_extension.js"></script>
  <script src="popup.js"></script>
</body>
</html>
  

6. Create popup.js:

    Plain Text
   
 

   import init, { greet } from './pkg/rust_chrome_extension.js';

async function main() {
  await init();
  
  document.getElementById('greet').addEventListener('click', () => {
    const name = document.getElementById('name').value;
    const output = greet(name);
    document.getElementById('output').textContent = output;
  });
}

main();
  

Building the Extension

1. Build the Rust code to WebAssembly:

    Plain Text
   
   wasm-pack build --target web

2. Load the extension in Chrome:

Open Chrome and navigate to chrome://extensions/
Enable "Developer mode"
Click "Load unpacked" and select your project directory

How It Works

Let's break down the key components:

1. Rust Code (lib.rs)

We use wasm-bindgen to create JavaScript bindings for our Rust function
The #[wasm_bindgen] attribute makes our function available to JavaScript
Our simple greet function takes a name parameter and returns a formatted string

2. HTML (popup.html)

Creates a basic UI with an input field and button
Loads the WebAssembly module and JavaScript code

3. JavaScript (popup.js)

Initializes the WebAssembly module
Sets up event listeners for user interaction
Calls our Rust function and displays the result

Testing the Extension

After loading the extension in Chrome:

Click the extension icon to open the popup
Enter a name in the input field
Click the "Greet" button
You should see a greeting message generated by the Rust code!

Demo

Here's what our extension looks like in action:

Sample output when you enter "Vivek" and click the Greet button:

Hello, Vivek! From Rust!

For a live demonstration and more examples, check out the demo folder in the GitHub repository.

Why Choose Rust for Chrome Extensions?

Building browser extensions with this system programming language offers compelling advantages that set it apart from traditional JavaScript-based development.

Here's a detailed breakdown of key benefits:

Feature	Description	Example
Performance	Native-speed execution through WebAssembly (WASM) compilation	Processing large datasets or images runs significantly faster than JavaScript, delivering superior user experience
Memory Safety	Advanced ownership model eliminates common bugs and vulnerabilities	Prevents null pointer dereferences and memory leaks that typically crash JavaScript extensions
Concurrency	Built-in support for safe multi-threading	Fetch data from multiple APIs simultaneously without race conditions
Cross-Browser Compatibility	WASM compilation ensures consistent performance across browsers	Your extension works seamlessly on Chrome, Firefox, and Edge
Framework Integration	Seamless handling of complex computations alongside modern front-end frameworks	Use React for UI while performing intensive calculations in the background

Additional benefits include:

Modern tooling: Access to a powerful ecosystem and efficient package management through cargo
Type system: Catch errors at compile time rather than runtime
Growing ecosystem: Expanding collection of libraries specifically for browser extension development
Future-proof: As WebAssembly evolves, this technology stack becomes increasingly valuable for web development

Complete Code

The complete source code for this tutorial is available on rust-chrome-extension.

Conclusion

We've successfully created a simple Chrome extension that leverages Rust and WebAssembly. While this example is basic, it demonstrates how to combine these technologies and sets the foundation for more complex extensions.

The combination of Rust's safety and performance with Chrome's extension platform opens up new possibilities for building powerful browser extensions. As WebAssembly continues to evolve, we can expect to see more developers adopting this approach.

Give it a try in your next Chrome extension project — you might be surprised by how easy it is to get started with Rust and WebAssembly!

Google Chrome WebAssembly Rust (programming language)

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