Wasm feature detect — npm.im/wasm-feature-detect

Your browser supports:

WebAssembly Feature Detection

A small library to detect which features of WebAssembly are supported.


npm install -g wasm-feature-detect


<script type="module">
  import { simd } from "https://unpkg.com/wasm-feature-detect?module";

  simd().then(simdSupported => {
    if (simdSupported) {
      /* SIMD support */
    } else {
      /* No SIMD support */

If required, there’s also a UMD version

<script src="https://unpkg.com/wasm-feature-detect/dist/umd/index.js"></script>
  wasmFeatureDetect.simd().then(/* same as above */);


All detectors return a Promise<bool>.

Function Proposal
bigInt() BigInt integration
bulkMemory() Bulk memory operations
exceptions() Exception handling
multiValue() Multi-value
mutableGlobals() Importable/Exportable mutable globals
referenceTypes() Reference Types
saturatedFloatToInt() Non-trapping float-to-int conversions
signExtensions() Sign-extension operators
simd() Fixed-Width SIMD
tailCall() Tail call
threads() Threads

Why are all the tests async?

The technical reason is that some tests might have to be augmented to be asynchronous in the future. For example, Firefox is planning to make a change that would require a postMessage call to detect SABs, which are required for threads.

The other reason is that you should be using WebAssembly.compile, WebAssembly.instantiate, or their streaming versions WebAssembly.compileStreaming and WebAssembly.instantiateStreaming, which are all asynchronous. You should already be prepared for asynchronous code when using WebAssembly!


If you want to contribute a new feature test, all you need to do is create a new folder in src/detectors and it will be automatically picked up. The folder must contain a module.wat file, which will be compiled using wabt.js.

;; Name: <Name of the feature for the README>
;; Proposal: <Link to the proposal’s explainer/repo>
;; Features: <Space-separated list of WasmFeatures from wabt.js>

  ;; More WAT code here

The folder can also contain an optional index.js file, whose default export must be an async function. This function can do additional testing in JavaScript and must return a boolean. See the “threads” detector as an example.

License Apache-2.0