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

• ✅ Runs in all major browsers
• ✅ Runs in Node
• ✅ Provided as an ES6 module, CommonJS and UMD module.
• ✅ CSP compatible
• ✅ Only ~520B gzipped

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 */
    }
  });
</script>

If required, there’s also a UMD version

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

All detectors return a Promise<bool>.

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 wat2wasm.

;; Name: <Name of the feature for the README>
;; Proposal: <Link to the proposal’s explainer/repo>
;; Flags: <CLI flags for `wat2wasm`>

(module
  ;; 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