emsdk

Emscripten SDK for npm. Install a specific Emscripten version with npm install and use emcc immediately — no manual SDK setup, no global installation.

Quick Start

# Install Emscripten 4.0.23
npm install [email protected]

# Compile C to WebAssembly
npx emcc hello.c -o hello.html

# Compile C++ to WebAssembly
npx em++ main.cpp -o main.js

The postinstall script automatically downloads the pre-built Emscripten toolchain (~300 MB) from Google Cloud Storage on first install.

Prerequisites

• Node.js 18+
• Python 3 (required by Emscripten's emcc compiler)
• macOS or Linux (Windows support planned)

How It Works

1. npm install [email protected] installs a small JS package and triggers postinstall
2. The postinstall script downloads the official pre-built Emscripten toolchain from Google Cloud Storage
3. The toolchain is extracted to the OS-native cache directory (shared across projects)
4. npx emcc, npx em++, and npx emrun are available immediately

Cache locations follow OS conventions:

| OS | Default path | |----|-------------| | macOS | ~/Library/Caches/emsdk/4.0.23/ | | Linux | ~/.cache/emsdk/4.0.23/ | | Windows | %LOCALAPPDATA%\emsdk\4.0.23\ |

The npm package version maps 1:1 to the Emscripten version.

CLI Usage

# Compile C to WebAssembly
npx emcc input.c -o output.js

# Compile C++ with optimizations
npx em++ -O2 main.cpp -o main.js

# Run a local web server for testing
npx emrun output.html

Programmatic API

const emsdk = require('emsdk');

// Get paths to tools
console.log(emsdk.emccPath());   // ~/Library/Caches/emsdk/4.0.23/install/emscripten/emcc (macOS)
console.log(emsdk.emppPath());   // ~/Library/Caches/emsdk/4.0.23/install/emscripten/em++ (macOS)

// Get environment variables for spawning processes
const env = emsdk.env();
// { EMSDK: '...', EM_CONFIG: '...', PATH: '...', ... }

// Run a tool programmatically
emsdk.run('emcc', ['hello.c', '-o', 'hello.js']);

// Check if installed
if (emsdk.isInstalled()) {
  console.log('Ready to compile!');
}

Configuration

Cache Location

The toolchain is cached in the OS-native cache directory by default. Override with:

EMSDK_CACHE=/custom/path npm install emsdk

Multiple Versions

Different projects can use different Emscripten versions:

# Project A
npm install [email protected]

# Project B
npm install [email protected]

Each version is cached separately in the OS cache directory.

Supported Platforms

| Platform | Architecture | Status | |----------|-------------|--------| | macOS | ARM64 (Apple Silicon) | Supported | | macOS | x64 (Intel) | Supported | | Linux | x64 | Supported | | Linux | ARM64 | Supported | | Windows | x64 | Planned |

License

MIT