Smalltalk in your browser

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Run Squeak, Pharo and Cuis images right in the browser — pure JavaScript, no plugins, no server. Built on SqueakJS, the original project, extended by Agustín Martínez with support for more Smalltalks and a Web-Worker runtime.

What you get

Pharo runs here. Pharo 10, both 32- and 64-bit, boots to a clean, fully interactive world. Getting there meant teaching the VM Pharo's file-attribute primitives, fixing how 64-bit images encode a method's program counter, and stepping around the parts of Pharo that expect native libraries the browser has no business providing — its git integration, for one.
Cuis 7.x runs here, thanks to reading the 16- and 64-bit array formats that the newer images rely on.
The page never freezes. The VM runs off the main thread, so the tab stays responsive even under heavy work — no spinner, no “ruedita”.
Image-managed cursor, flicker-free rendering, dynamic resize, sound, and the system clipboard.
Save straight to Downloads, and open files by drag-and-drop or a 📂 button — which also works on mobile.

Run an image from your device

Drag a Smalltalk image onto this page (together with its changes and sources files, if any) to run it.

Show a 📂 button to open files — needed on mobile, where drag-and-drop isn't available.

Drop images and other files here, or

Files are stored in your browser's database; clicking a name above exports it to your Downloads.

Or run one of these from the internet

Squeak — 6.0
Cuis — 7.8 (from the official repo)
Pharo — 10 (32-bit) · 10 (64-bit) · live Morphic demo (straight from files.pharo.org)
Dialog.ar — example drawing app for kids

First run downloads and caches the image in your browser; later starts are much faster. If a bundle ships both a 32- and 64-bit image, the 32-bit build is used. Pharo and Cuis are fetched from their own official repositories, so you always get the current build. GitHub sends the CORS headers a browser requires; files.pharo.org does not, so those downloads go through a small proxy of ours — the bytes still come from Pharo's servers. Only the compatibility startup scripts (a few KB) are hosted here.

About Pharo: both builds boot to a clean, fully interactive world. Pharo's git/Iceberg integration needs native FFI (unavailable in the browser), so SqueakJS skips that startup step instead of letting it open a debugger — Pharo simply runs without git, exactly as on a machine without libgit2. Pharo's 64-bit builds ship SDL2-only and dropped the classic display/input classes, so their bundle carries a compatibility startup.st that restores them; to run your own 64-bit image, keep that file next to it. The live Morphic demo is the 32-bit image opening a small self-contained app at startup — the full IDE stays one menu-bar click away.

Embed it on your own site

This run/ launcher is the reference: copy it and point it at your image. It runs the VM in a Web Worker and wires input, cursor, clipboard, sound, save-to-Downloads and the file picker. At its core:

<canvas id="sq"></canvas>
<script type="module">
  const canvas = document.getElementById("sq");
  canvas.width = innerWidth; canvas.height = innerHeight;
  const offscreen = canvas.transferControlToOffscreen();
  const worker = new Worker("squeak_worker.js", { type: "module" });
  worker.postMessage({
    type: "init", canvas: offscreen,
    width: canvas.width, height: canvas.height,
    image: "my.image",   // a URL, or the image bytes (ArrayBuffer)
    name:  "/my.image",  // full path, including .image
  }, [offscreen]);
  // then forward mouse/keyboard and handle cursor/clipboard/sound —
  // see run/index.html for the complete wiring.
</script>

For a classic single-thread embed you can still use SqueakJS.runSqueak("my.image", canvas, {…}) from squeak.js.

Simpler still, drop the launcher into an <iframe> and everything comes wired — see it running here, with Dialogo embedded in an ordinary page.

Credits & source

SmalltalkJsVm is free software (MIT). It builds on SqueakJS, the original project; the Pharo and Cuis 7.x compatibility work, the Web Worker runtime and the usability additions live in this fork by Agustín Martínez. Bug reports and pull requests welcome.

Have fun! — SmalltalkJsVm is free software (MIT).