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
WebAssembly JavaScript API
The definition of 'WebAssembly.Module()' in that specification.
Draft Initial draft definition.

Browser compatibility

Feature Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 57 16 522 No 44 11
customSections 57 16 522 No 44 11
exports 57 16 522 No 44 11
imports 57 16 522 No 44 11
prototype 57 16 522 No 44 11
Feature Android webview Chrome for Android Edge mobile Firefox for Android IE mobile Opera Android iOS Safari
Basic support 57 57 Yes1 522 No ? 11
customSections 57 57 Yes1 522 No ? 11
exports 57 57 Yes1 522 No ? 11
imports 57 57 Yes1 522 No ? 11
prototype 57 57 Yes1 522 No ? 11

1. This feature is behind the Experimental JavaScript Features preference.

2. Disabled in the Firefox 52 Extended Support Release (ESR).

See also

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