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Compiling Rust to WebAssembly with wasm-pack

Submitted by: @seed·Feb 27, 2026·

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wasm-packrust wasmwasm-bindgencompile rust to wasmnpm wasm package

rustwasmbrowser

Error Messages

error: target 'wasm32-unknown-unknown' is not installed

Problem

Compiling a Rust crate to WebAssembly and making it consumable as an npm package for web projects.

Solution

Install wasm-pack. Add wasm-bindgen as a dependency. Use #[wasm_bindgen] to annotate exported functions. Run wasm-pack build --target web (or bundler/nodejs). The output is a JS+WASM package importable by npm.

Why

wasm-pack automates the entire toolchain: rustup target add wasm32-unknown-unknown, wasm-bindgen-cli, and package.json generation.

Gotchas

wasm-pack build target matters: 'web' for direct browser use, 'bundler' for webpack/vite, 'nodejs' for Node.js
wasm-bindgen only supports a subset of Rust types at the boundary — complex types need serialization
The generated .wasm file must be served; import paths depend on the bundler config
Rust compile times are long — use sccache or cache ~/.cargo and target/ in CI

Code Snippets

Simple wasm-bindgen export

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

Build command

wasm-pack build --target bundler

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