Despite its growing popularity, there are several common misconceptions about WebAssembly that need to be addressed. Let's have a look at what WebAssembly is not to better understand its true purpose and capabilities.
WebAssembly was never designed to replace JavaScript. Instead, it was created to complement JavaScript by working alongside it, combining the performance benefits of compiled languages with JavaScript's flexibility! The two technologies form a powerful synergy, with WebAssembly modules being loadable through JavaScript's API.
A common misconception is that WebAssembly can only run in web browsers. Although "Web" is part of its name, WebAssembly is not limited to browsers. It's designed to be a platform-independent technology that can run in various environments, including IoT devices, edge computing, artificial intelligence, game development, backend services, or cloud services. Its portable binary format allows it to execute efficiently across different platforms and architectures.
WebAssembly modules run in a sandbox environment that isolates them from the rest of the system. That's why WebAssembly modules cannot access anything outside their own memory space, such as browser APIs like the DOM or other Web APIs, file system or networking. While this may seem limiting, it's a crucial security feature that prevents malicious code from accessing sensitive resources or interfering with other parts of the application. To work with external resources, WebAssembly modules must go through JavaScript as an intermediate layer, and engines nowadays have Wasm-specific optimizations in place so that this intermediate layer has almost no overhead. Therefore, frameworks like Leptos and Yew can provide seamless abstractions for working with browser APIs while being written entirely in languages that compile to WebAssembly. These frameworks handle all the JavaScript interop internally, enabling developers to build efficient web applications in their preferred language while maintaining full access to browser functionality - all without compromising the security guarantees of the sandbox.
While C, C++, and Rust were among the first languages to support WebAssembly compilation, it's not exclusive to these languages. As WebAssembly evolves and adds new features like garbage collection, more languages are gaining WebAssembly support. Languages like Dart, Flutter, Kotlin, Python, C#, Go, and many others now have varying levels of WebAssembly support. While Go also supports WebAssembly compilation, it currently ships with its own garbage collector rather than using WebAssembly's built-in garbage collection feature.
The addition of features like garbage collection and exception handling in WebAssembly makes it more accessible to high-level languages that rely on these features. This is particularly important for languages with managed memory, as they previously had to ship their own garbage collectors, leading to larger binary sizes and potential performance overhead.
Furthermore, the WebAssembly ecosystem continues to grow with tools and frameworks that make it easier for different programming languages to target WebAssembly. Projects like Emscripten, wasm-bindgen, and wasm-pack have made it simpler for developers from various language backgrounds to compile their code to WebAssembly and integrate it with web applications.
While WebAssembly offers near-native performance, it's not automatically faster than JavaScript in all scenarios. Modern JavaScript engines like V8 use sophisticated multi-tier compilation architectures with advanced optimizations that make JavaScript execution extremely fast. These engines use techniques like just-in-time compilation, inline caching, and adaptive optimization to achieve impressive performance for most web applications. WebAssembly's performance benefits are most noticeable in computationally intensive tasks that require heavy calculations, complex algorithms, or tight loops with predictable types. For many standard web applications focused on DOM manipulation, event handling, and basic business logic, the performance difference might be negligible or even favor JavaScript due to the highly optimized nature of modern JS engines and the overhead of crossing the JS-WebAssembly boundary.
Some might worry about running compiled code in their browser, but WebAssembly was designed with security as a primary concern. It executes in a sandboxed environment with strict security boundaries. WebAssembly modules can't directly access system resources unless explicitly granted by the host environment, making it a safe technology for running untrusted code.