"Rust for WebAssembly: How to Build High-Performance Web Apps with Rust"

Are you tired of sluggish web applications that take ages to load? Do you want to build apps that feel like native applications, but run on the web? Enter Rust for WebAssembly!

WebAssembly, or wasm for short, is a low-level bytecode that can be executed in the browser. It promises to bring native-like performance to the web and is quickly gaining traction in the web development community. With wasm, you can write in any language that compiles to wasm and works in the browser, including Rust!

Rust is a systems programming language that is rapidly gaining popularity among developers for its speed, memory safety, and concurrency features. Rust can be used to build everything from operating systems to web applications.

In this article, we'll explore how to build high-performance web applications using Rust and WebAssembly.

Why Rust for WebAssembly?

Rust is a great choice for WebAssembly for several reasons:

Memory Safety

Memory safety is critical for web applications. Rust prevents programming errors like buffer overflows, dangling pointers, and data races at compile time, making it easier to write safe and secure web applications.


Rust is a high-performance programming language. It is designed to provide control over machine resources and optimal performance. Rust is also known for its ability to write code that is faster than C++. Combining Rust with WebAssembly really puts your application performance in the fast lane!


Concurrency is essential when building web applications to improve their responsiveness. Rust provides great support for concurrency with its lightweight and efficient concurrency model.

Developer Productivity

Finally, Rust has a straightforward syntax, strong typing, and extensive documentation making it easy to learn and use, translating to better productivity and efficiency for developers.

Getting Started with Rust for WebAssembly

To get started with Rust for WebAssembly, you'll need to have the following installed:

Once you have these tools installed, you're ready to create a new Rust project!

Creating a New Rust Project

To create a new Rust project, open your terminal and navigate to the directory where you'd like to create your project. Then, run the following commands:

cargo new --bin mywebapp
cd mywebapp

This creates a new Rust binary project called mywebapp.

Converting Rust Code to WebAssembly

Now that you have a new Rust project, you can convert your Rust code to WebAssembly.

Adding Dependencies

To get started with WebAssembly, we need to add the wasm-bindgen dependency to our project. This package helps bridge the gap between WebAssembly and JavaScript.

To add the wasm-bindgen dependency, open your Cargo.toml file, and add the following lines:

crate-type = ["cdylib"]

wasm-bindgen = "0.2.68"

The [lib] section specifies the type of the output library; in this case, we're using the cdylib type. The [dependencies] section specifies the wasm-bindgen package.

Writing Rust Code

Let's create a simple Rust function that we can convert to WebAssembly. Open the src/main.rs file and add the following code:

pub fn add(a: i32, b: i32) -> i32 {
    a + b

In this code, we've defined a public function called add that takes two i32 arguments and returns their sum as an i32.

The #[no_mangle] attribute is necessary to prevent Rust from mangling the function name, which would make it difficult to call from JavaScript.

Compiling Rust to WebAssembly

Now that we've written our Rust code, we can compile it to WebAssembly using the following command:

cargo +nightly build --target wasm32-unknown-unknown

This command tells cargo to build the project using the nightly toolchain (+nightly) and to build our project for the WebAssembly architecture (--target wasm32-unknown-unknown).

After the build runs successfully, you'll find a new file in the target/wasm32-unknown-unknown/debug directory called mywebapp.wasm. This is your compiled WebAssembly code!

Importing WebAssembly in JavaScript

To use the compiled WebAssembly code, we need to import it in our JavaScript. For that, we'll use the wasm-loader package:

npm install --save-dev wasm-loader

Next, create a new JavaScript file called index.js in the root directory of your project and add the following code:

import wasmModule from './mywebapp/pkg/mywebapp.js';

(async () => {
  const wasm = await wasmModule();
  console.log(wasm.add(2, 2));

In this code, we're importing the WebAssembly code from our mywebapp package and calling the add function with two arguments. We're using a self-executing async function to wait for the WebAssembly module to load before running the code.

Now, if you run npm start or open the index.html from the previous section, you should see 4 in the console!


Rust for WebAssembly is a powerful tool for building high-performance web applications. Rust provides the memory safety, performance, and concurrency features that are essential for modern web applications.

With Rust and WebAssembly, you can write code that is blazing fast and that feels like a native application while still running in the browser!

So, what are you waiting for? Start exploring the world of Rust and WebAssembly and build amazing web applications that perform like never before!

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