WebAssembly is a new type of code that can be run in modern web browsers — it is a low-level assembly-like language with a compact binary format that runs with near-native performance and provides languages such as C/C++ with a compilation target so that they can run on the web. It is also designed to run alongside JavaScript, allowing both to work together.

In a Nutshell

WebAssembly has huge implications for the web platform — it provides a way to run code written in multiple languages on the web at near native speed, with client apps running on the web that previously couldn’t have done so.

WebAssembly is designed to complement and run alongside JavaScript — using the WebAssembly JavaScript APIs, you can load WebAssembly modules into a JavaScript app and share functionality between the two. This allows you to take advantage of WebAssembly's performance and power and JavaScript's expressiveness and flexibility in the same apps, even if you don't know how to write WebAssembly code.

And what's even better is that it is being developed as a web standard via the W3C WebAssembly Working Group and Community Group with active participation from all major browser vendors.

Guides

WebAssembly concepts
Get started by reading the high-level concepts behind WebAssembly — what it is, why it is so useful, how it fits into the web platform (and beyond), and how to use it.
Compiling a New C/C++ Module to WebAssembly
When you’ve written code in C/C++, you can then compile it into .wasm using a tool like Emscripten. Let’s look at how it works.
Compiling an Existing C Module to WebAssembly
A core use-case for WebAssembly is to take the existing ecosystem of C libraries and allow developers to use them on the web.
Compiling from Rust to WebAssembly
If you've written some Rust code, you can compile it into WebAssembly! This tutorial takes you through all you need to know to compile a Rust project to wasm and use it in an existing web app.
Loading and running WebAssembly code
After you have a .wasm, this article covers how to fetch, compile and instantiate it, combining the WebAssembly JavaScript API with the Fetch or XHR APIs.
Using the WebAssembly JavaScript API
Once you've loaded a .wasm module, you'll want to use it. In this article we show you how to use WebAssembly via the WebAssembly JavaScript API.
Exported WebAssembly functions
Exported WebAssembly functions are the JavaScript reflections of WebAssembly functions which allow calling WebAssembly code from JavaScript. This article describes what they are.
Understanding WebAssembly text format
This article explains the wasm text format. This is the low-level textual representation of a .wasm module shown in browser developer tools when debugging.
Converting WebAssembly text format to wasm
This article provides a guide on how to convert a WebAssembly module written in the text format into a .wasm binary.

API reference

WebAssembly
This object acts as the namespace for all WebAssembly related functionality.
WebAssembly.Global()
A WebAssembly.Global object represents a global variable instance, accessible from both JavaScript and importable/exportable across one or more WebAssembly.Module instances. This allows dynamic linking of multiple modules.
WebAssembly.Module()
A WebAssembly.Module object contains stateless WebAssembly code that has already been compiled by the browser and can be efficiently shared with Workers, and instantiated multiple times.
WebAssembly.Instance()
A WebAssembly.Instance object is a stateful, executable instance of a ModuleInstance objects contain all the Exported WebAssembly functions that allow calling into WebAssembly code from JavaScript.
WebAssembly.instantiateStreaming()
The WebAssembly.instantiateStreaming() function is the primary API for compiling and instantiating WebAssembly code, returning both a Module and its first Instance.
WebAssembly.Memory()
A WebAssembly.Memory object is a resizable ArrayBuffer that holds the raw bytes of memory accessed by an Instance.
WebAssembly.Table()
A WebAssembly.Table object is a resizable typed array of opaque values, like function references, that are accessed by an Instance.
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

Specifications

Specification Status Comment
WebAssembly JavaScript Interface Working Draft Initial draft definition of the JavaScript API.

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung 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

Last updated by: johnstevenson,