raku.online — a Raku playground that runs in your browser

20 July 2026

raku.online — a Raku playground that runs in your browser

Last week we announced Raku++, our new Raku compiler, and Raku.js, its WebAssembly build. Today they get their own home on the web: raku.online — a Raku playground that runs entirely in your browser.

Try it right now, nothing to install: raku.online.

A Raku program loaded in the raku.online playground — source code on the left, its output on the right

What it is

raku.online is a playground for the Raku programming language. The interpreter is Raku++, our C++ implementation of Raku, compiled to WebAssembly. There is no back end: your program runs in a Web Worker on your own machine, and the whole site is just five static files.

Your code never leaves the browser. Nothing is sent to a server and nothing is stored server-side.
Instant and offline. Once the page has loaded, you can run Raku with no network at all — press Run, get output, and a Stop button that actually stops.
Standard input, too. A collapsible Stdin strip under the editor feeds get, lines, prompt, and $*IN, fresh on every run.

Share a program with a link

The 🔗 Share button packs your code straight into the URL — deflate-compressed and base64url-encoded — so a link is the program. Send it to a colleague and they open your exact code, ready to run. Nothing is stored anywhere; the link carries everything.

You can also open code from elsewhere: a GitHub gist, a file in a GitHub repo, or any HTTPS URL that allows cross-origin fetches. Add &run=1 and it runs on load:

https://raku.online/?gh=ash/rakupp/main/examples/anagrams.raku&run=1

Put runnable Raku on your own site

The same engine ships as a drop-in widget, raku.js. Add one script tag, and any code block you mark becomes a live, editable, runnable editor:

<script src="https://raku.online/raku.js"></script>

<pre data-raku>say "Hello from an embedded editor!";</pre>

Each editor lives in its own Shadow DOM, so it looks identical on any site and never clashes with the host page's styles. Every editor on a page shares a single Web Worker and one WebAssembly instance, so ten code blocks download the interpreter only once. With data-auto, ordinary highlighted raku code blocks become runnable automatically — and the embed builder turns pasted code into a ready-to-paste snippet with a live preview.

That is exactly how spec.raku.online works: every example in the specification is a live, runnable editor, embedded straight into the page.

An embedded, runnable Raku code block showing arithmetic operators and their output

An embedded, runnable Raku code block showing the ternary operator and its output

An embedded, runnable Raku code block showing the list-repetition operator and its output

Open source

raku.online is open source and lives on GitHub: github.com/ash/raku.online. Because it is self-contained static files, you can host the whole playground yourself or embed pieces of it anywhere you write about Raku.

It is also the fastest way to try the language — and the engine behind the instant playground of the Raku Course. Read more on the raku.online page.

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