MDN wants to learn about developers like you:

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The WebAssembly.validate() function validates a given typed array of WebAssembly binary code, returning whether the bytes form a valid wasm module (true) or not (false).




A typed array or ArrayBuffer containing WebAssembly binary code to be validated.

Return value

A boolean that specifies whether bufferSource is valid wasm code (true) or not (false).


If bufferSource is not a typed array or ArrayBuffer, a TypeError is thrown.


The following example (see the validate.html source code, and see it live too) fetches a .wasm module and converts it into a typed array. The validate() method is then used to check whether the module is valid.

fetch('simple.wasm').then(response =>
).then(function(bytes) {
  var valid = WebAssembly.validate(bytes);
  console.log("The given bytes are "
    + (valid ? "" : "not ") + "a valid wasm module");


Specification Status Comment
Web Assembly JavaScript API
The definition of 'validate()' in that specification.
Draft Initial draft definition.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 57 15[2] 52 (52)[1] No support 44 11
Feature Chrome for Android Android Webview Edge Mobile Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support 57 57 No support 52.0 (52)[1] No support No support 11

[1] WebAssembly is enabled in Firefox 52+, although disabled in the Firefox 52 Extended Support Release (ESR.)

[2] Currently supported behind the “Experimental JavaScript Features” flag. See this blog post for more details.

See also

Document Tags and Contributors

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