⚙️ 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
# wrangler.toml
wasm_bindings = [
  { name = "MODULE1", path="module1.wasm" },
  { name = "MODULE2", path="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:

# wrangler.toml
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.