WebAssembly.Module() constructor

A WebAssembly.Module() constructor creates a new Module object containing stateless WebAssembly code that has already been compiled by the browser and can be efficiently shared with Workers, and instantiated multiple times.

The WebAssembly.Module() constructor function can be called to synchronously compile given WebAssembly binary code. However, the primary way to get a Module is through an asynchronous compilation function like WebAssembly.compile().

Note: Webpages that have strict Content Security Policy (CSP) might block WebAssembly from compiling and executing modules. For more information on allowing WebAssembly compilation and execution, see the script-src CSP.


Warning: Since compilation for large modules can be expensive, developers should only use the Module() constructor when synchronous compilation is absolutely required; the asynchronous WebAssembly.compileStreaming() method should be used at all other times.

new WebAssembly.Module(bufferSource)



A typed array or ArrayBuffer containing the binary code of the .wasm module you want to compile.


  • If the parameter is not of the correct type or structure, a TypeError is thrown.
  • If compilation fails, the constructor rejects with a WebAssembly.CompileError.
  • Some browsers may throw a RangeError, as they prohibit compilation and instantiation of Wasm with large buffers on the UI thread.


Synchronously compiling a WebAssembly module

const importObject = {
  imports: {
    imported_func(arg) {

function createWasmModule(bytes) {
  return new WebAssembly.Module(bytes);

  .then((response) => response.arrayBuffer())
  .then((bytes) => {
    const mod = createWasmModule(bytes);
    WebAssembly.instantiate(mod, importObject).then((result) =>


WebAssembly JavaScript Interface
# dom-module-module

Browser compatibility

BCD tables only load in the browser

See also