ClojureWasm Playground

Run Clojure in your browser, evaluated by ClojureWasm (cljw) — a from-scratch Clojure runtime in Zig, no JVM. Submissions are evaluated in-process on the server's cljw under a per-submission budget (steps / deadline / heap), and can call sandboxed WebAssembly modules written in Rust and Go via cljw's Wasm FFI.

The Wasm FFI now runs JIT-compiled by default (cljw v1.0.0, embedding zwasm v2.0.0): (wasm/load …) transparently rides zwasm's :auto JIT-first engine, so a tight numeric loop inside a module executes as native machine code — the engine-select and jit-speed examples show a ten-million-step loop returning in a few milliseconds, byte-identical to the interpreter. The engine is a runtime default; pass {:engine :interp} / {:engine :jit} to pick one explicitly.

What's inside

• Frontend (src/, ClojureScript + shadow-cljs) — a CodeMirror editor + a Wasm-module reference panel. The optimized release bundle is committed at resources/public/js/main.js.
• Backend (server/, ClojureWasm) — playground.server serves the SPA and a /api/eval endpoint; playground.sandbox bounds each submission with cljw.eval/with-budget. Runs on cljw, no JVM, no Babashka.
• Wasm modules (modules/, hand-written Rust + Go) — exposed to evaluated code via (wasm/load …) / (wasm/run …). Origins in PROVENANCE.md.

Run it

./run_local.sh        # builds cljw from source on first run, serves http://localhost:8080

Deploy to fly.io (or any container host) — see DEPLOY.md. The repo is self-contained: only cljw is built from source (Zig); the SPA and Wasm modules are committed artifacts.

License

See the ClojureWasm project for runtime licensing. Demo sources here are provided as-is for illustration.