The WebAssembly JavaScript object acts as the namespace for all WebAssembly-related functionality.

Unlike most other global objects, WebAssembly is not a constructor (it is not a function object). You can compare it to Math, which is also a namespace object for mathematical constants and functions, or to Intl which is the namespace object for internationalization constructors and other language sensitive functions.

Description

The primary uses for the WebAssembly object are:

Methods

WebAssembly.instantiate()
The primary API for compiling and instantiating WebAssembly code, returning both a Module and its first Instance.
WebAssembly.instantiateStreaming()
Compiles and instantiates a WebAssembly module directly from a streamed underlying source, returning both a Module and its first Instance.
WebAssembly.compile()
Compiles a WebAssembly.Module from WebAssembly binary code, leaving instantiation as a separate step.
WebAssembly.compileStreaming()
compiles a WebAssembly.Module directly from a streamed underlying source, leaving instantiation as a separate step.
WebAssembly.validate()
Validates a given typed array of WebAssembly binary code, returning whether the bytes are valid WebAssembly code (true) or not (false).

Constructors

WebAssembly.Global()
Creates a new WebAssembly Global object.
WebAssembly.Module()
Creates a new WebAssembly Module object.
WebAssembly.Instance()
Creates a new WebAssembly Instance object.
WebAssembly.Memory()
Creates a new WebAssembly Memory object.
WebAssembly.Table()
Creates a new WebAssembly Table object.
WebAssembly.CompileError()
Creates a new WebAssembly CompileError object.
WebAssembly.LinkError()
Creates a new WebAssembly LinkError object.
WebAssembly.RuntimeError()
Creates a new WebAssembly RuntimeError object.

Examples

The following example (see our instantiate-streaming.html demo on GitHub, and view it live also) directly streams a .wasm module from an underlying source then compiles and instantiates it, the promise fulfilling with a ResultObject. Because the instantiateStreaming()  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) } };

WebAssembly.instantiateStreaming(fetch('simple.wasm'), importObject)
.then(obj => obj.instance.exports.exported_func());

The ResultObject's instance member is then accessed, and the contained exported function invoked.

Specifications

Specification Status Comment
WebAssembly JavaScript Interface
The definition of 'WebAssembly' in that specification.
Working Draft Initial draft definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
CompileErrorChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
GlobalChrome Full support 69Edge No support NoFirefox Full support 62IE No support NoOpera No support NoSafari No support NoWebView Android Full support 69Chrome Android Full support 69Edge Mobile No support NoFirefox Android Full support 62Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
InstanceChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
LinkErrorChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
MemoryChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
ModuleChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
RuntimeErrorChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
TableChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
compileChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android Full support 44Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
compileStreamingChrome Full support 61Edge Full support 16Firefox Full support 58IE No support NoOpera Full support 47Safari No support NoWebView Android Full support 61Chrome Android Full support 61Edge Mobile No support NoFirefox Android Full support 58Opera Android ? Safari iOS No support NoSamsung Internet Android No support Nonodejs No support No
instantiateChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0
instantiateStreamingChrome Full support 61Edge Full support 16Firefox Full support 58IE No support NoOpera Full support 47Safari No support NoWebView Android Full support 61Chrome Android Full support 61Edge Mobile No support NoFirefox Android Full support 58Opera Android ? Safari iOS No support NoSamsung Internet Android No support Nonodejs No support No
validateChrome Full support 57Edge Full support 16Firefox Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
IE No support NoOpera Full support 44Safari Full support 11WebView Android Full support 57Chrome Android Full support 57Edge Mobile Full support Yes
Disabled
Full support Yes
Disabled
Disabled This feature is behind the Experimental JavaScript Features preference.
Firefox Android Full support 52
Notes
Full support 52
Notes
Notes Disabled in the Firefox 52 Extended Support Release (ESR).
Opera Android ? Safari iOS Full support 11Samsung Internet Android Full support 7.0nodejs Full support 8.0.0

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Document Tags and Contributors

Contributors to this page: chrisdavidmills, fscholz, emilbayes, apurv-pandey, lukewagner
Last updated by: chrisdavidmills,