WebAssembly and wasip1

Updated

September 8, 2026

WebAssembly and wasip1

Overview

Go can target js/wasm (browser + wasm_exec.js) and wasip1 (WASI preview1) for server-side Wasm runtimes. Constraints differ sharply from linux/amd64.

Diagram: Wasm targets

  Go source
     ├── GOOS=js   GOARCH=wasm ──► browser + wasm_exec
     └── GOOS=wasip1 GOARCH=wasm ──► WASI runtime

Targets

GOOS=js GOARCH=wasm go build -o main.wasm .
GOOS=wasip1 GOARCH=wasm go build -o main.wasm .

Constraints

Area	Reality
Threads	Limited / host-dependent
Networking	WASI and browser models differ
Filesystem	Capability-based under WASI
cgo	Generally unavailable
Binary size	Larger than tiny Go-less Wasm; use strip/trimpath

Use Cases

Policy plugins
Edge filters
Portable CLI sandboxes
Browser tools (js/wasm)

Experiment

# if wasip1 supported:
printf 'package main\nimport "fmt"\nfunc main(){ fmt.Println("hi wasm") }\n' > /tmp/w.go
cd /tmp && GOOS=wasip1 GOARCH=wasm go build -o hi.wasm w.go
ls -la hi.wasm
# run with a WASI runtime if installed, e.g. wasmtime hi.wasm

What to notice: Build succeeds without a local WASI runner; size is non-trivial compared to a hello C program.

Try next: Compare GOOS=wasip1 vs native binary size with -ldflags='-s -w'.