Gaurav Varma

With Ruby 3.2, developers can now compile Ruby code to WebAssembly using WASI (WebAssembly System Interface). This marks a significant step toward making Ruby applications portable across platforms like browsers, edge devices, and even serverless runtimes.

What is WASI?

WASI stands for WebAssembly System Interface — a standardized set of APIs that give WebAssembly modules access to system-like features such as files, clocks, environment variables, and more. It allows WebAssembly to run in environments outside the browser safely and securely.

Why Ruby in WebAssembly?

Historically, Ruby has been tightly coupled to its native system runtime. This made it difficult to run Ruby scripts in sandboxed environments like browsers or edge compute services. But with WASI support, you can now:

Embed Ruby scripts in WebAssembly runtimes
Run Ruby in the browser (with limited I/O)
Deploy Ruby logic to edge functions or CDNs
Experiment in isolated, reproducible environments

This is a foundational shift, enabling Ruby to be more portable, embeddable, and accessible in polyglot environments.

How to Try It

The Ruby core team has created ruby.wasm — a project that compiles Ruby to WebAssembly and provides tools to run it in WASI-compatible runtimes.

Here’s how to get started:

1git clone https://github.com/ruby/ruby.wasm
2cd ruby.wasm
3make setup
4make build

You can also try it directly in the browser via the hosted playground:

👉 https://livecodes.io

Or run .wasm files using runtimes like Wasmtime or Wasmer:

1wasmtime ruby.wasm --eval 'puts "Hello from WASI Ruby!"'

Use Cases

Interactive Ruby tutorials in the browser
WASM-powered Ruby CLIs embedded in web UIs
Edge deployments with tools like Fastly or Cloudflare Workers (WASI-based)
Ruby playgrounds and sandboxes for teaching or demos

While you can’t yet run a full Rails app in WASM, this opens the door to future frameworks or mini-Rack-style implementations in the browser.

Limitations

Ruby’s WASI support is still experimental. A few limitations include:

No support for threads, sockets, or some native gems
Limited system calls and file system access
Only basic I/O support via stdout and stdin

Still, it's promising — especially for lightweight Ruby logic and experimentation.

References

Final Thoughts

Ruby 3.2’s WASI support is one of the boldest moves toward modernizing Ruby’s deployment story. While still early, it represents a new era — where Ruby can live beyond servers, breaking into browsers, embedded platforms, and serverless worlds.

Ruby 3.2 adds WebAssembly (WASI) support to the Ruby VM