Testing Regular Expressions Efficiently
Regular expressions are powerful but error-prone — a misplaced quantifier or forgotten escape can match nothing or match everything. Our regex tester gives you instant visual feedback: write a pattern, paste test text, and see matches highlighted in real time. No compilation, no test scripts, no guessing.
The tester uses JavaScript's regex engine, so the behavior matches exactly what you'll get in Node.js, browser JavaScript, and TypeScript. It supports all flags: g (global), i (case-insensitive), m (multiline), s (dotAll), and u (Unicode). Captured groups are displayed separately so you can verify your extraction logic.
Common use cases: validating email/phone patterns, extracting data from log lines, parsing URLs and query strings, writing input validation for forms, and building text processing pipelines. The live feedback loop makes iteration fast — change one character and instantly see the effect.
Tips
- Start with a simple pattern and build complexity gradually — it's easier to debug that way.
- Use named groups
(?<name>...)for readable extraction:/(?<year>\d{4})-(?<month>\d{2})/. - Escape special characters with
\: to match a literal dot, use\.not.. - Beware of catastrophic backtracking — patterns like
(a+)+$can hang on certain inputs.