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⚙️ WebAssembly


WebAssembly modules are bound as follows. The bound keys will be instances of WebAssembly.Module:

$ miniflare --wasm MODULE1=module1.wasm --wasm MODULE2=module2.wasm
MODULE1 = "module1.wasm"
MODULE2 = "module2.wasm"
const mf = new Miniflare({
wasmBindings: {
MODULE1: "module1.wasm",
MODULE2: "module2.wasm",

You can then use the WebAssembly modules in your workers:

const instance = new WebAssembly.Instance(MODULE1);
addEventListener("fetch", (e) => {
// Assuming MODULE1 exports a function `add` summing 2 integer arguments
const value = instance.exports.add(1, 2);
e.respondWith(new Response(value.toString()));


You can also import WebAssembly modules by adding a CompiledWasm module rule. See 📚 Modules for more details. For instance, with the following wrangler.toml file and worker script, we can achieve the same result as the previous example:

type = "CompiledWasm"
globs = ["**/*.wasm"]
import module1 from "./module1.wasm";
const instance = new WebAssembly.Instance(module1);
export default {
fetch() {
const value = instance.exports.add(1, 2);
return new Response(value.toString());

Rust Wrangler Builds

When using Rust Wrangler Builds, wasm is automatically bound to your compiled WebAssembly module.