Lua Playground

Under the hood. Lua runs on Fengari, a pure-JavaScript Lua 5.3 interpreter (vendored locally, no CDN at runtime). The interpreter runs in a Web Worker, so a runaway loop doesn't freeze the page — anything over 5 seconds is terminated automatically.
What's missing. No filesystem, no network, and the io and os libraries are intentionally not loaded (nothing to open, nothing to shell out to). This is a sandbox for Lua the language, not the runtime around it.