Lean tutorials — proofs checked in your browser

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λ Lean tutorials

Proofs are checked by the real Lean kernel compiled to WebAssembly, running on your device. Runtime and packed Lean library come from lean.cau.li (cauli/lean4-wasm-in-browser, Apache-2.0). Nothing you type is sent anywhere.

First visit downloads about 47 MB of runtime (brotli-compressed). After that it is cached and starts instantly.