{"slug": "lean-in-the-browser", "title": "Lean in the Browser", "summary": "Developer Kshitij Lakhina published a working WebAssembly build of Lean 4 and its language server, hosted at kshitijl/lean-wasm, with a browser demo at /demos/lean-wasm/demo/. Lakhina built it to support an in-progress interactive game that teaches Lean to programmers through specs and proofs for code rather than math. The demo does not work on phones; Chrome performs best, Firefox works but is slower, and Safari is unstable and slow.", "body_md": "# Lean in the browser\n\nI 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).\n\nI 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.\n\nIn 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.\n\nThere’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.", "url": "https://wpnews.pro/news/lean-in-the-browser", "canonical_source": "https://klauria.tech/lean-wasm/", "published_at": "2026-11-13 20:43:24+00:00", "updated_at": "2026-11-13 20:50:08.094490+00:00", "lang": "en", "topics": ["developer-tools"], "entities": ["Lean 4", "Kshitij Lakhina", "kshitijl/lean-wasm", "WebAssembly", "Chrome", "Firefox", "Safari"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/lean-in-the-browser", "markdown": "https://wpnews.pro/news/lean-in-the-browser.md", "text": "https://wpnews.pro/news/lean-in-the-browser.txt", "jsonld": "https://wpnews.pro/news/lean-in-the-browser.jsonld"}}