Build ruby.wasm

ruby.wasm is a collection of WebAssembly ports of the CRuby. It enables running Ruby application on browsers, WASI compatible WebAssembly runtimes, and Edge Computing platforms.

Try ruby.wasm (no installation needed)

Try ruby.wasm in TryRuby in your browser.

Quick Example: Ruby on Web browser

Create and save index.html page with the following contents:

  <script src="[email protected]/dist/browser.script.iife.js"></script>
  <script type="text/ruby">
    require "js"

    puts RUBY_VERSION # (Printed to the Web browser console)[:document].write "Hello, world!"

Quick Example: How to package your Ruby application as a WASI application

Dependencies: wasmtime

$ gem install ruby_wasm
# Download a prebuilt Ruby release
$ curl -LO
$ tar xfz ruby-3.3-wasm32-unknown-wasip1-full.tar.gz

# Extract ruby binary not to pack itself
$ mv ruby-3.3-wasm32-unknown-wasip1-full/usr/local/bin/ruby ruby.wasm

# Put your app code
$ mkdir src
$ echo "puts 'Hello'" > src/my_app.rb

# Pack the whole directory under /usr and your app dir
$ rbwasm pack ruby.wasm --dir ./src::/src --dir ./ruby-3.3-wasm32-unknown-wasip1-full/usr::/usr -o my-ruby-app.wasm

# Run the packed scripts
$ wasmtime my-ruby-app.wasm /src/my_app.rb

npm packages (for JavaScript host environments)

See the of each package for more detail and its usage.

Package Description npm
@ruby/3.3-wasm-wasi CRuby 3.3 built on WASI with JS interop support npm version
@ruby/3.2-wasm-wasi CRuby 3.2 built on WASI with JS interop support npm version
@ruby/head-wasm-wasi HEAD CRuby built on WASI with JS interop support npm version
@ruby/head-wasm-emscripten HEAD CRuby built on Emscripten (not well tested) npm version

Prebuilt binaries

This project distributes prebuilt Ruby binaries in GitHub Releases. A build is a combination of ruby version, profile, and target.

Supported Target Triples

Triple Description
wasm32-unknown-wasip1 Targeting WASI Preview1 compatible environments
(e.g. Node.js, browsers with polyfill, wasmtime, and so on)
wasm32-unknown-emscripten Targeting JavaScript environments including Node.js and browsers


Profile Description
minimal No standard extension libraries (like json, yaml, or stringio)
full All standard extension libraries

Notable Limitations

The current WASI target build does not yet support Thread related APIs. Specifically, WASI does not yet have an API for creating and managing threads yet.

Also there is no support for networking. It is one of the goal of WASI to support networking in the future, but it is not yet implemented.


See for how to build and test, and how to contribute to this project. Bug reports and pull requests are welcome on GitHub at