Regex Tester

About Regex Tester

A regex tester lets you check a regular expression against sample text and see exactly what it matches. Enter a pattern and flags, paste your text, and matches highlight in real time with numbered and named capture groups broken out. Invalid patterns are reported instead of throwing, and everything runs in your browser.

Frequently asked questions

Which regex flavor does this use?

JavaScript's regular expression engine, including flags like g (global), i (case-insensitive), m (multiline), s (dotall), and u (unicode).

Does it support named capture groups?

Yes. Named groups like (?<year>\d{4}) are captured and shown alongside numbered groups.

Why does my global pattern only match once elsewhere?

Zero-length matches under the global flag can loop; this tester advances safely past them so every match is found without hanging.