terminal Python Editor (Run in Browser) star

How It Works

This runs an actual CPython interpreter — the same reference implementation your desktop python3 command is built from — compiled to WebAssembly via Pyodide, loaded once into your browser and executed entirely on your device. Your code never reaches this site's server; there's no sandboxed subprocess on a backend, no queued job, nothing to upload. The first run downloads the Python runtime (roughly 12 MB), which your browser then caches, so every run after that — and every run on a later visit — starts instantly instead of re-downloading anything.

Because it's genuine CPython rather than a simulated subset, Python's real semantics apply exactly as they would locally. That includes its defining syntax rule: Python determines block structure — where a function body, loop, or if-branch begins and ends — purely from indentation level, unlike C, Java or JavaScript, which use {} braces for the same purpose. Mixing tabs and spaces within one block is exactly the kind of thing this real interpreter will reject with an IndentationError rather than silently guessing, because Python 3 refuses to run code whose indentation is ambiguous.

Good to Know

The full Python standard library ships with the runtime — math, json, re, datetime, and the rest — so anything that only needs the standard library runs unmodified. Third-party packages from PyPI are a separate matter: they're not preloaded, since bundling them would balloon the initial download for every visitor regardless of whether they need them.