Is my Python code uploaded to a server?

No. The compiler uses Pyodide — the real CPython interpreter compiled to WebAssembly — which runs inside your own browser tab. Your code is executed locally and is never sent to induwara.lk or anywhere else. You can confirm this in DevTools → Network: after the one-time runtime download, running code makes zero network requests.

Which Python version is this?

It runs CPython 3.x via Pyodide (currently the 0.27 series). The full standard library is available — math, json, datetime, re, random, collections, itertools and so on — because it's the actual CPython interpreter, not a re-implementation.

Why does the first run take a few seconds?

The first time you press Run, the browser downloads the Python runtime (~10 MB) from a CDN and initialises it. That happens once — after it's cached, subsequent runs start almost instantly. A status line shows the loading progress.

Can I use NumPy, Pandas or other packages?

Pyodide can load many scientific packages (NumPy, Pandas, SciPy, scikit-learn) and pure-Python wheels from PyPI via micropip. This playground ships a clean interpreter for fast loading; package installation is on the roadmap. The standard library works out of the box today.

Does input() for interactive programs work?

Interactive stdin (input()) isn't wired up in this browser playground, since there's no terminal attached. For exercises that need input, set the values directly in your code as variables. Everything that prints to stdout/stderr shows in the output panel.

Is there a time limit, and what happens to infinite loops?

Each run has a 15-second limit and runs in a Web Worker, so an accidental infinite loop is stopped automatically and your browser tab stays responsive. You can also hit Stop at any time. Output is capped so a runaway print loop can't freeze the page.

Is this good for learning / A-Level ICT?

Yes — it's a zero-setup way to practise Python from any device, including a phone. No install, no account, nothing to configure. Write a snippet, run it, see the result. It's ideal for students testing concepts, teachers demonstrating code, or anyone wanting a quick scratchpad.

Developer · Runs in your browser

Online Python Compiler — run Python 3 in your browser

Write Python and run it instantly, free, with no signup. It uses real CPython compiled to WebAssembly, so everything executes in your own browser — your code never leaves your device.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated May 28, 2026

Python 3 · runs in your browser

Loading editor…

Output

Press Run to execute. Output appears here.

How it works

This compiler runs Pyodide— the standard CPython interpreter compiled to WebAssembly. When you press Run, your code executes inside a sandboxed Web Worker in your browser, not on our server. That means it's private (nothing is uploaded), it scales infinitely (your device does the work), and it can never reach our systems or other users.

Because it's the real interpreter, the full Python standard library behaves exactly as it does on your machine — print, f-strings, comprehensions, classes, exceptions, json, math, and more. The first run downloads the runtime once (~10 MB) and caches it; after that, runs are near-instant.

Execution is wrapped in a 15-second timeout and an output cap. If code runs too long (an infinite loop, say), the worker is terminated automatically and the tab stays usable — a guarantee you only get by running in a worker rather than the main thread.

Frequently asked questions

Sources & references

Execution is the unmodified CPython interpreter via Pyodide WebAssembly; only the editor and worker glue are custom.

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Found a bug or want another language added?

Email me at [email protected].