Regex Tester

This tool uses JavaScript's built-in RegExp engine, which supports most standard regex syntax including lookaheads, named capture groups, and Unicode mode.

g = global (find all matches), i = case insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines), u = Unicode mode.

Groups wrapped in () capture the matched text. Named groups use (?<name>...) syntax. Captured values appear in the match details panel.

Patterns that can match zero-length strings (like a* or .*) can loop infinitely. The tool has a built-in safety limit of 10,000 matches to prevent this.

Yes. All regex matching happens in your browser. Nothing is sent to a server.