Regex Tester
Test and debug regular expressions live. Highlights matches, shows groups.
\d — digit (0–9)
\w — word char (a-z, A-Z, 0-9, _)
\s — whitespace
\b — word boundary
. — any char (except newline)
^ / $ — start / end of string
[abc] — character class
[^abc] — negated class
a|b — alternation (a or b)
(...) — capture group
(?:...) — non-capturing group
(?<name>...) — named group
* / + / ? — quantifiers
{n,m} — repeat n to m times
*? / +? — lazy quantifiers
(?=...) — positive lookahead
(?!...) — negative lookahead
(?<=...) — positive lookbehind
(?<!...) — negative lookbehind
About Regex Tester
Regex Tester lets you write, test, and debug regular expressions entirely in your browser. Paste your pattern, choose flags (global, case-insensitive, multiline, dotAll), type a test string, and instantly see every match highlighted in different colors. Each match card shows the matched value, character index range, and any captured groups — including named groups. Switch to Replace mode to preview substitutions with $1-style back-references. All processing is done locally with the browser's native RegExp engine. Nothing is sent anywhere.