HTML: Markup language
CSS: Styling language
JavaScript: Scripting language
Web APIs: Programming interfaces
All web technology
Learn web development
Discover our tools
Get to know MDN better
This feature is well established and works across many devices and browser versions. It’s been available across browsers since October 2017.
* Some parts of this feature may have varying levels of support.
The WebAssembly.compile() static method compiles WebAssembly binary code into a WebAssembly.Module object. This function is useful if it is necessary to compile a module before it can be instantiated (otherwise, the WebAssembly.instantiate() function should be used).
WebAssembly.compile()
WebAssembly.Module
WebAssembly.instantiate()
Note: Webpages that have strict Content Security Policy (CSP) might block WebAssembly from compiling and executing modules. For more information on allowing WebAssembly compilation and execution, see the script-src CSP.
WebAssembly.compile(bufferSource) WebAssembly.compile(bufferSource, compileOptions)
bufferSource
A typed array or ArrayBuffer containing the binary code of the Wasm module you want to compile.
ArrayBuffer
compileOptions
An object containing compilation options. Properties can include:
builtins
An array of one or more strings that enables the usage of JavaScript builtins in the compiled Wasm module. The strings define the builtins you want to enable. Currently the only available value is "js-string", which enables JavaScript string builtins.
"js-string"
importedStringConstants
A string specifying a namespace for imported global string constants. This property needs to be specified if you wish to use imported global string constants in the Wasm module.
A Promise that resolves to a WebAssembly.Module object representing the compiled module.
Promise
TypeError
WebAssembly.CompileError
The following example compiles the loaded simple.wasm byte code using the compile() function and then sends it to a worker using postMessage().
compile()
const worker = new Worker("wasm_worker.js"); fetch("simple.wasm") .then((response) => response.arrayBuffer()) .then((bytes) => WebAssembly.compile(bytes)) .then((mod) => worker.postMessage(mod));
Note: You'll probably want to use WebAssembly.compileStreaming() in most cases, as it is more efficient than compile().
WebAssembly.compileStreaming()
This example enables JavaScript string builtins and imported global string constants when compiling the Wasm module with compile(), before instantiating it with instantiate() then running the exported main() function (which logs "hello world!" to the console). See it running live.
instantiate()
main()
"hello world!"
const importObject = { // Regular import m: { log: console.log, }, }; const compileOptions = { builtins: ["js-string"], // Enable JavaScript string builtins importedStringConstants: "string_constants", // Enable imported global string constants }; fetch("log-concat.wasm") .then((response) => response.arrayBuffer()) .then((bytes) => WebAssembly.compile(bytes, compileOptions)) .then((module) => WebAssembly.instantiate(module, importObject)) .then((instance) => instance.exports.main());
Enable JavaScript to view this browser compatibility table.