WebAssembly

WebAssembly touches Go in two directions: compiling Go to Wasm, and running Wasm modules inside a Go program. The standard toolchain supports both browser output with GOOS=js GOARCH=wasm and WASI with GOOS=wasip1, added in Go 1.21. The libraries here fill gaps around those targets: smaller binaries, browser APIs, testing, and runtimes for hosting Wasm plugins.

TinyGo is the main alternative compiler; it produces much smaller Wasm files than the standard toolchain and also targets microcontrollers, at the cost of partial standard library and reflection support. For browser code, dom, webapi and go-canvas provide typed access to DOM and Canvas APIs instead of raw syscall/js calls, and vert converts between Go and JavaScript values. wasmbrowsertest runs go test inside a real browser. For hosting, wasmtime-go binds the Wasmtime runtime through cgo, and the Extism Go SDK builds plugin systems on top of a Wasm runtime.

To ship Go to the browser, test whether binary size matters for your users; if it does, TinyGo is usually the answer. To run untrusted or polyglot plugins inside a Go service, a Wasm runtime gives you sandboxing that Go's own plugin package does not. Note that several browser binding packages here have not been updated in years.