A typed, total functional programming language designed to compile to multiple targets.
Write and run Bosatsu code directly in your browser. Experiment with the language without installing anything.
Try the Compiler →See the same Bosatsu program compiled to JavaScript, C, and WebAssembly. Experience the power of multi-target compilation.
View Demo →See JavaScript and WebAssembly working together. One module compiled to JS, another to WASM, calling each other at runtime.
View Interop Demo →Learn Bosatsu syntax, types, and features. Explore the standard library and language reference.
Read Docs →Reactive UI without Virtual DOM. Compile-time static analysis extracts state-to-DOM bindings for O(1) updates.
Basic counter showing direct DOM binding updates. Watch the binding log to see O(1) state-to-DOM updates.
Try Counter →Per-item bindings for O(1) updates even in large lists. Toggle, add, delete todos with targeted DOM updates.
Try Todo List →BosatsuUI vs React 18 performance comparison. Uses actual React (not simulated) for fair results.
Run Benchmarks →Interactive calculators with "Why?" explanations and "What if?" explorations. Generated from .bosatsu source files.
Calculate monthly payments and total interest. Click "Why?" to see the derivation chain. Use sliders to explore scenarios.
Try Loan Calculator →Compute taxes with derivation tracking. See how each value is calculated from your inputs.
Try Tax Calculator →Estimate your annual CO2 emissions from transportation and home energy. See which factors have the biggest impact.
Try Carbon Calculator →