For learners · Free

Write code that actually runs, not just gets checked.

Practise real interview problems and run real code in 9 languages, from JavaScript to Rust. Free, no account needed.

Illustration with sample data

Run

Practice

Solve real interview problems in the browser. Your code is actually compiled and run against test cases — never just pattern-matched.

77 problems · 9 languages · a real compiler, not a guess

Read

Interview-prep articles on JavaScript, Python, C#, SQL and system design, split into short chapters you can read in one sitting each.

25 topics

Build

Build small interfaces from a brief and compare your result against the reference. Front-end practice with a live preview.

22 challenges

A sequence through Learn, Practice and UI Challenges in one sensible order instead of a pile of unconnected problems, with a finish line at the end.

8 paths

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