A small Ruby runtime for a very large edge

Ruby at the edge. The web you know.

Write a Rack-style application in PicoRuby. Compile it to WebAssembly. Run it inside Cloudflare Workers, close to every request.

Get started View on GitHub

REQUEST /hello EDGE READY

01 Cloudflare Request

02 Wasm ABI v3

03 PicoRuby Rack app

class App
  def self.call(env)
    [200, { "content-type" => "text/plain" },
      ["Hello from the edge"]]
  end
end

ruby bytecode loaded 200 OK · 12ms

Rackprotocol adapter

JSPIasync host bridge

Wasmcompact runtime

1 VMper request

01 — THE POSSIBILITY

Ruby ergonomics.
Edge-native reach.

PicoRuby brings a compact Ruby implementation to WebAssembly. The adapter connects familiar Ruby application shapes to Cloudflare’s global runtime and request-scoped platform bindings.

Keep the Ruby shape

A familiar call(env) entrypoint and a Rack response tuple let application code stay recognizably Ruby.

Reach the platform

Use D1, KV, R2, Workers AI, Vectorize, Queues, Durable Objects, Access, and Web Crypto from request-scoped Ruby wrappers.

Stay intentionally small

Precompiled bytecode, one VM per request, and explicit compatibility boundaries make the runtime understandable and testable.

02 — GETTING STARTED

One command to a new edge app.

Install the generator gem and create a minimal Worker project. The CLI writes the Ruby app, build configuration, Worker entrypoint, package manifests, and Wrangler configuration for you.

Ruby ≥ 3.2Node.jsEmscripten ≥ 5.0.0PicoRuby

Template & CLI repository

quickstart.sh

01gem install picoruby-cloudflare-template
02picoruby-cloudflare new hello-edge
03cd hello-edge bundle install && npm install
04export PICORUBY_ROOT=/path/to/picoruby npm run dev

❯ Ready on http://localhost:8787

03 — RACK & SINATRA

A narrow bridge,
built on purpose.

The runtime implements the Rack application protocol—an environment Hash in, a [status, headers, body] tuple out. It is not the complete CRuby Rack distribution.

Read the compatibility contract

class App
  def self.call(env)
    name = env["PATH_INFO"].split("/").last
    [200,
      { "content-type" => "text/plain" },
      ["Hello, #{name}!"]]
  end
end

Rackup::Handler::CloudflareWorker.run(App)

class App < Sinatra::Base
  get "/hello/:name" do
    content_type "text/plain"
    "Hello, #{params[:name]} from PicoRuby"
  end
end

Rackup::Handler::CloudflareWorker.run(App)

Runtime contractCURRENT