The WebAssembly.compileStreaming() function compiles a WebAssembly.Module directly from a streamed underlying source.  This function is useful if it is necessary to a compile a module before it can be instantiated (otherwise, the WebAssembly.instantiateStreaming() function should be used).


Promise<WebAssembly.Module> WebAssembly.compileStreaming(source);


A Response object or a promise that will fulfill with one, representing the underlying source of a .wasm module you want to stream and compile.

Return value

A Promise that resolves to a WebAssembly.Module object representing the compiled module.



The following example (see our compile-streaming.html demo on GitHub, and view it live also) directly streams a .wasm module from an underlying source then compiles it to a WebAssembly.Module object. Because the compileStreaming()  function accepts a promise for a Response object, you can directly pass it a WindowOrWorkerGlobalScope.fetch() call, and it will pass the response into the function when it fulfills.

var importObject = { imports: { imported_func: arg => console.log(arg) } };

.then(module => WebAssembly.instantiate(module, importObject))
.then(instance => instance.exports.exported_func());

The resulting module instance is then instantiated using WebAssembly.instantiate(), and the exported function invoked.


Specification Status Comment
WebAssembly features for web embedding
The definition of 'compileStreaming()' in that specification.
Draft Initial draft definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support61 No58 No47 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support6161 No58 ? No No

See also

Document Tags and Contributors

 Contributors to this page: chrisdavidmills
 Last updated by: chrisdavidmills,