Languages to Wasm

Writing WAT by hand is a great way to learn the Wasm execution model, but in practice you compile from a real programming language. The compiler takes care of register allocation, memory layout, and binary encoding — you write idiomatic code and get a .wasm file.

This module covers the four toolchains most commonly used today, compares their tradeoffs, and gives you real build commands for each.

The four toolchains at a glance

Language	Toolchain	Output size	Best for
Rust	`wasm-pack` / `wasm-bindgen`	Small (no GC, no runtime)	New Wasm-first code, npm packages
C / C++	Emscripten (`emcc`)	Medium–large (libc emulation)	Porting existing C/C++ libraries
AssemblyScript	`asc`	Very small	TypeScript developers, simple modules
TinyGo	`tinygo build`	Small	Go developers, microcontrollers

How each toolchain maps to Wasm

flowchart LR
  subgraph Sources
    R["Rust<br/>.rs files"]
    C["C / C++<br/>.c .cpp files"]
    AS["AssemblyScript<br/>.ts files"]
    TG["TinyGo<br/>.go files"]
  end
  subgraph Toolchain
    WP["wasm-pack<br/>(wasm-bindgen)"]
    EM["Emscripten<br/>(emcc)"]
    ASC["asc<br/>(AssemblyScript compiler)"]
    TIGO["tinygo build"]
  end
  subgraph Output
    WASM[".wasm binary"]
    GLUE["JS glue (optional)"]
  end
  R --> WP --> WASM
  C --> EM --> WASM
  C --> EM --> GLUE
  AS --> ASC --> WASM
  TG --> TIGO --> WASM

Language → toolchain → .wasm

Key differences

Rust with wasm-bindgen generates rich JS/Wasm bindings automatically. You can pass strings, JS objects, and callbacks across the boundary without writing any glue code by hand. Binary size is small because Rust has no garbage collector or runtime heap.

Emscripten emulates a POSIX-like environment inside Wasm. This means C code that uses printf, malloc, or file I/O often compiles with zero changes. The tradeoff is a larger output that includes libc emulation and an optional JS loader.

AssemblyScript compiles a strict subset of TypeScript directly to Wasm. There is no need to learn a new language — if you know TypeScript you can be productive immediately. The compiler is fast and produces very compact binaries.

TinyGo compiles a subset of Go to Wasm (and to microcontrollers). It is a good fit for teams that already write Go and want to share logic with a web frontend. Not all standard library packages are supported.