An app for learning regular expressions by writing them. You type a pattern and it highlights every match in the test text as you type, so the feedback is immediate rather than guessed at. Structured challenges climb from literals and character classes through quantifiers, groups, alternation and lookarounds, and each answer is checked against cases that must match and cases that must not — a solution has to be genuinely correct, and the failing cases show what to fix.
- A sandbox for testing any pattern against any text, with a library of ready-made patterns for emails, dates and IP addresses.
- A reference for the syntax you forget, from \b to lookarounds.
- Saved patterns, challenge progress and a practice streak, all kept on the device.
- Runs entirely offline. No account, no connection, no advertising, no analytics.