react-native-android-webassembly

Android module for running WebAssembly through androidx.javascriptengine.

This package exports a standard WebAssembly ponyfill for React Native. It is designed as a drop-in replacement for browser-style WebAssembly.* usage, and it keeps .wasm binaries out of the JS bundle by loading them from Metro assets at runtime.

Public API

• WebAssembly
• Module
• Instance
• Memory
• Table
• Global
• Tag
• Exception
• CompileError
• LinkError
• RuntimeError
• makeImportClosure(...)
• polyfillGlobalWebAssembly()
• clearWasmHandles()

Asset loading

Treat .wasm files as Metro assets, then resolve the asset URI and pass the bytes into WebAssembly.instantiate() or WebAssembly.compile().

import {WebAssembly} from 'react-native-android-webassembly';

const asset = require('./assets/my-module.wasm');
const uri =
  typeof asset === 'string'
    ? asset
    : asset?.uri ?? require('react-native/Libraries/Image/resolveAssetSource').default(asset).uri;

const response = await fetch(uri);
const bytes = await response.arrayBuffer();
const {instance} = await WebAssembly.instantiate(bytes);

If you want the ponyfill to be available on globalThis, call polyfillGlobalWebAssembly() once during app startup.

Example app

The repository includes an emulator-ready app under example/ that exercises the standard WebAssembly API, including asset-backed module loading and the WPT compatibility harness.

Run the Metro server:

npm run example:start

Install and launch on Android:

npm run example:android

For the fastest local development loop, link the package into the example once after installing dependencies:

npm run example:link

Tests

Unit tests currently live in test/assetUri.test.js and run with:

npm test