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QuickRef.dev

Run code online. Look up syntax. Move on.

A free online code playground and pocket reference for Python, JavaScript, SQL and HTML. Everything runs in your browser: no install, no account, no queue.

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Run code online

main.pyPython› print([n * n for n in range(5)])[0, 1, 4, 9, 16]Real CPython 3, stdin, stdlib main.jsJavaScript› console.log([3, 1, 2].toSorted())[ 1, 2, 3 ]Console, top-level await query.sqlSQL› SELECT city, COUNT(*) FROM customers GROUP BY city;London | 2SQLite + sample shop DB index.htmlHTML/CSS/JS› <button>Click me</button>live preview ↻Three panels, live preview

Cheat sheets

Grouped by task, with copy buttons. Python, JavaScript and SQL snippets run with one click.

All 19 cheat sheets

AI code generator

“Find all .log files older than 7 days and gzip them”

find /var/log/myapp -name "*.log" -mtime +7 \
  -exec gzip {} \;

Describe what you need in plain English and get one clean snippet in Python, JavaScript, SQL, Bash, Docker, Git and more. Every playground also has Explain and Fix the error buttons.

Generate code

Explainers you can poke at

The concepts behind the most-searched syntax, built so you change something and watch what happens.

SQL joinsSwitch INNER, LEFT, FULL, anti and CROSS joins and watch rows survive or turn to NULL.List comprehensionsStep item by item through the loop, the filter and the result.async / awaitTrace the call stack, microtasks and timers to see why the output comes out in that order.f-string formatsBuild a Python format spec from its parts and see the exact output.
/\d+/gRegex tester
Live highlighting, capture groups, a plain-English breakdown of every token, and an AI “describe it” mode.→ 3Python visualizer
Replay a program line by line with the call stack and every variable shown. Real CPython, private, in your browser.✓ pyPython code checker
Find syntax errors with the exact line and column, plus names that are never defined, without running the code..dbSQLite viewer
Open a .db or .sqlite file, browse its tables and run SQL on it. The file never leaves your device.{ }JSON formatter
Beautify, minify and validate, with the exact line and column of any error and a one-click fix for trailing commas.

Frequently asked questions

Is QuickRef.dev free?

Yes. The playgrounds, cheat sheets and tools are free with no account. The AI features are free within a fair-use rate limit.

Which languages can I run online here?

Python 3 (real CPython via WebAssembly), JavaScript, SQL (SQLite) and HTML/CSS/JS with a live preview. All of them run in your browser, not on a server.

Do I need to install anything?

No. Open a playground and press Run. The Python runtime downloads once (about 12 MB) and is cached by your browser after that.

Is my code private?

Code you run stays on your device. It is only sent to an AI model if you press one of the AI buttons (Generate, Explain, Fix).