What is WebAssembly?

WebAssembly (often shortened to Wasm) is a low-level code format that browsers can run very fast, almost like native machine code. It lets developers write programs in languages like C, Rust, or Go and then use them on the web alongside JavaScript.

Let's break it down

  • Low-level code format: Think of it as a simplified version of the computer’s own language, but designed to be safe and portable.
  • Browsers can run very fast: WebAssembly is compiled ahead of time, so the browser doesn’t have to interpret it line by line like it does with JavaScript.
  • Almost like native machine code: It runs at speeds close to what you’d get from a program installed directly on your computer.
  • Write programs in other languages: Instead of being forced to use JavaScript, you can code in languages you already know (C, Rust, etc.) and then convert the code to WebAssembly.
  • Use them on the web alongside JavaScript: WebAssembly doesn’t replace JavaScript; it works together with it, letting each do what it’s best at.

Why does it matter?

WebAssembly makes heavy-duty tasks-like video editing, 3D graphics, or scientific calculations-run smoothly in a web page, opening the door for richer, faster web apps without requiring users to download separate software.

Where is it used?

  • Gaming: Browser-based games that need high performance, such as ports of Unity or Unreal Engine titles.
  • Image and video editing: Online tools that manipulate large media files quickly (e.g., photo editors, video transcoding services).
  • Scientific and engineering simulations: Web apps that run complex calculations for physics, chemistry, or data analysis.
  • Legacy software: Running old desktop applications (like CAD tools) directly in the browser by compiling them to Wasm.

Good things about it

  • Near-native speed performance.
  • Language flexibility - you can bring existing C/C++/Rust code to the web.
  • Secure sandboxed execution, preventing unsafe memory access.
  • Small binary size, which downloads faster than equivalent JavaScript bundles.
  • Works in all major browsers without plugins.

Not-so-good things

  • Limited access to browser APIs compared to JavaScript; you still need JS to handle many UI tasks.
  • Debugging can be harder because the code runs in a compiled form.
  • Larger initial learning curve for developers unfamiliar with low-level languages or the Wasm toolchain.
  • Not ideal for small, simple scripts where JavaScript is already sufficient.