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A rollup plugin that inlines (base64 encoded) and imports WebAssembly modules
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grinat and jamen fix: broken wasm in browser (#15)
Changed custom base64 implementation in banner to window.atob for browsers and Buffer.from for node
Latest commit b7abab0 Feb 11, 2019



Rollup plugin for importing WebAssembly modules.

Use this Rollup plugin to import WebAssembly modules and bundle them as base64 strings. They are imported async (but small modules can be imported sync).


npm i -D rollup-plugin-wasm


Add the plugin to your rollup config and then any imported .wasm file will be processed by it.

import wasm from 'rollup-plugin-wasm'

export default {
  input: 'web/index.js',
  plugins: [


Given the following simple C file (compiled using emscripten, or the online WasmFiddle tool):

int main() {
  return 42;

Import and instantiate the resulting file:

import wasm from './sample.wasm';

sample({ ...imports }).then(({ instance }) => {

The WebAssembly is inlined as a base64 encoded string (which means it will be ~33% larger than the original). At runtime the string is decoded and a module is returned.

Sync Modules

Small modules (< 4KB) can be compiled synchronously by specifying them in the configuration.

  sync: [

This means that the exports can be accessed immediately.

import module from './sample.wasm'

const instance = sample({ ...imports })

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