Choosing a Language

Every Wasm toolchain reaches the same finish line — a .wasm binary that runs in the browser — but each follows a different road. The right choice depends on your existing codebase, your team’s skills, and the constraints of your project.

Decision table

Question	Rust	C / Emscripten	AssemblyScript	TinyGo
Team already writes this language?	Maybe	Maybe	If you know TS	If you know Go
Existing codebase to port?	No	Yes	No	No
Binary size priority?	Excellent	Large (libc overhead)	Excellent	Good
GC / runtime overhead?	None	Libc only	None	Minimal
Rich JS interop (strings, objects)?	Yes (wasm-bindgen)	Via ccall/cwrap	Via loader	Limited
Standard library coverage?	Full std	Full libc	Limited	Partial
Async / concurrency support?	Via futures	Via Asyncify	Limited	Limited
Learning curve (Wasm-specific)?	Medium	Low (if you know C)	Very low (TS)	Low (if you know Go)

Rust — when to choose it

Choose Rust when you are writing new Wasm-first code and want:

The smallest possible binary (no GC, no runtime heap).
Automatic, type-safe JS bindings via wasm-bindgen.
A crate ecosystem designed for wasm32-unknown-unknown.
Publishable npm packages from wasm-pack.

wasm-pack build --target web
# → pkg/ ready to npm publish

C / C++ with Emscripten — when to choose it

Choose Emscripten when you are porting an existing C/C++ library and need:

printf, malloc, file I/O, and POSIX APIs to work without changes.
OpenGL emulation via WebGL (-sUSE_WEBGL2).
A single-step build from a standard Makefile or CMake project.

emcc existing_lib.c -o out.js -sEXPORTED_FUNCTIONS='["_my_api"]' -O2

AssemblyScript — when to choose it

Choose AssemblyScript when your team writes TypeScript and you need:

A very gentle learning curve (same syntax, different numeric types).
A tiny, self-contained Wasm module with no dependencies.
Fast iteration without setting up a Rust or C toolchain.

npx asc assembly/index.ts --outFile build/release.wasm --optimize

TinyGo — when to choose it

Choose TinyGo when your team writes Go and you want to share pure-logic packages between a Go backend and a browser frontend:

tinygo build -o wasm.wasm -target wasm ./main.go

Note: TinyGo does not support the full Go standard library. Packages that use net, os, or reflection may not compile. Check the TinyGo package support table before committing.

Quick-pick flowchart

Have C/C++ code that already works? → Emscripten.
Team writes TypeScript and wants a quick win? → AssemblyScript.
Team writes Go? → TinyGo.
Writing new code and want the best binary size + JS interop? → Rust.

Trade-offs

Option	Benefit	Cost
Rust + wasm-bindgen	Memory safety from the ownership model, very small binaries, no GC	Steeper learning curve than the others — you need to understand ownership/borrowing
C/C++ + Emscripten	Huge C/C++ ecosystem, port an existing codebase almost immediately	Glue code and the POSIX emulation layer add runtime overhead, producing a larger binary
AssemblyScript	Familiar syntax for a TypeScript team, fastest to get started	Much smaller ecosystem, and not semantically identical to TypeScript — the type system differs

Common mistakes

Choosing a language purely by team familiarity without checking the resulting binary size — e.g. using Emscripten for a small module with no existing codebase to port, shipping a runtime far bigger than needed
Shipping an unoptimized Emscripten build — not stripping the POSIX emulation layer and not using flags like -O3 or -sMINIMAL_RUNTIME — so the bundle bloats
Treating AssemblyScript as if it were all of TypeScript, then using syntax or semantics asc doesn’t support, hitting a compile error or a hard-to-track bug

💡 Real-world example

Figma chose C++ with Emscripten for the rendering engine it ported from desktop, measuring more than a 3x improvement in load time after the switch (Figma engineering blog). Shopify Functions, by contrast, lets merchants write custom checkout logic that compiles to Wasm — currently in Rust or JavaScript (Shopify Functions docs) — two examples that picked different languages for different requirements.