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.

A WebAssembly.Module object contains stateless WebAssembly code that has already been compiled by the browser and can be efficiently shared with Workers, cached in IndexedDB and instantiated multiple times. The WebAssembly.Module() constructor function can be called to synchronously compile given WebAssembly binary code. However, the primary way to get a Module is through an asynchronous compilation function like WebAssembly.compile() or by reading a Module out of IndexedDB.

Constructor Syntax

Important: Since compilation for large modules can be expensive, developers should only use the Module() constructor when synchronous compilation is absolutely required; the asynchronous WebAssembly.compile() method should be used at all other times.

var myModule = new WebAssembly.Module(bufferSource);


A typed array or ArrayBuffer containing the binary code of the .wasm module you want to compile.

Function Properties of the Module Constructor

Given a Module and string, returns a copy of the contents of all custom sections in the module with the given string name.
Given a Module, returns an array containing descriptions of all the declared exports.
Given a Module, returns an array containing descriptions of all the declared imports.

Module instances

All Module instances inherit from the Module() constructor's prototype object — this can be modified to affect all Module instances.

Instance properties

Returns the function that created this object's instance. By default this is the WebAssembly.Module() constructor.
The initial value of the @@toStringTag property is the String value "WebAssembly.Module".

Instance methods

Module instances have no default methods of their own.


Specification Status Comment
Web Assembly JavaScript API
The definition of 'WebAssembly.Module()' 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

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