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WebAssembly

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Description #

WebAssembly (Wasm) is a low-level, binary instruction format designed to run at near-native speed in web browsers. It allows developers to compile code written in languages like C, C++, and Rust into a format that can be executed safely and efficiently on the web.

History #

WebAssembly was announced in 2015 as a joint effort by major browser vendors including Mozilla, Google, Microsoft, and Apple. Its goal was to provide a secure, portable, and high-performance alternative to JavaScript for computation-heavy applications. Wasm became an official web standard in 2019, and is now supported by all major browsers.

Key milestones:

  • 2015: Project announced by W3C
  • 2017: MVP (Minimum Viable Product) shipped in major browsers
  • 2019: Became a W3C recommendation (official standard)
  • Continues to evolve with support for threads, garbage collection, and more

Hello World Code #

watCopyEdit(module
  (func $hello (export "hello")
    (nop)
  )
)

Or in a higher-level language like C (compiled to Wasm):

#include <stdio.h>
int main() {
  printf("Hello, World!\n");
  return 0;
}

How to Run #

Using WebAssembly Studio:

  1. Visit https://webassembly.studio
  2. Choose a template (e.g., C → Wasm)
  3. Edit code and click “Build and Run”

Using command-line tools (for C/C++):

  1. Install Emscripten
  2. Compile:
emcc hello.c -o hello.html

Key Concepts #

  • .wasm is the binary format; .wat is the human-readable format
  • Sandboxed execution for security
  • Language-agnostic (supports C, Rust, Go, etc.)
  • Interacts with JavaScript via the WebAssembly API
  • Compiled ahead-of-time for performance
  • Ideal for games, image processing, and simulations
  • Can be used outside browsers via WASI (WebAssembly System Interface)
  • Faster startup and predictable performance
  • Safe memory model (linear memory)
  • Supported in all major browsers

Try It Online #

Fun Facts #

  • WebAssembly is designed to complement, not replace, JavaScript
  • It runs at near-native speeds in the browser
  • You can compile entire game engines like Unity to Wasm
  • Wasm binaries are usually smaller and faster than JavaScript
  • The .wasm file format is platform-independent and runs safely in any environment that supports it

Resources #

Updated on June 7, 2025

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