# Lean in the Browser

> Source: <https://klauria.tech/lean-wasm/>
> Published: 2026-11-13 20:43:24+00:00

# Lean in the browser

I hacked together a working wasm build of Lean 4 and its language server. For details on how it works see [kshitijl/lean-wasm](https://github.com/kshitijl/lean-wasm).

I did it to make an interactive game that teaches Lean *to programmers*, so it’s focused on specs and proofs for code rather than math. That’s still work in progress as I figure out the material, levels and so forth.

In the meantime, here’s a demo of Lean in the browser! For now it doesn’t work on phones. Chrome is best, Firefox works but is slower, Safari is unstable and pretty slow.

There’s also a full page demo at [/demos/lean-wasm/demo/](https://klauria.tech/demos/lean-wasm/demo/index.html) since embedding it here makes it pretty narrow.