About RegexLab
RegexLab is a small, focused regular-expression tester. Instead of a bloated multi-tool, it does one thing well: it helps you write, test, debug and understand regular expressions, right in your browser.
Every calculation runs entirely on the device, using your browser's native RegExp engine. There are no accounts, no ads following you around, and no analytics that sell your behaviour. The patterns and text you type never leave your device.
It is built and maintained by Interhive OÜ, a small studio in Tallinn that makes tiny, dependable web tools.
What's inside
- ›Live match highlighting with capture-group and offset details
- ›All six flags: global, ignore-case, multiline, dotAll, unicode and sticky
- ›Replace / substitution preview with $1, $2 backreferences
- ›Plain-language explanation of every token in your pattern
- ›A library of ready-made patterns: email, URL, IPv4, UUID, dates and more
- ›Friendly error messages on invalid patterns