Code Tower · room 9
Regex Tester
Test regular expressions with live match highlighting and replace.
🔒 Processed in your browser · No upload · No sign-up
Test JavaScript regular expressions live
Type a pattern and see every match highlighted instantly, with capture groups (including named groups like (?<year>\d{4})), match positions and a replace preview. The tester uses your browser's JavaScript regex engine, so results match what String.prototype.match and replace do in Node.js and browsers.
Flags
g finds all matches, i ignores case, m makes ^ and $ match at line breaks, s lets . match newlines, u enables full Unicode and \p{…} classes, and y matches only at lastIndex.
Performance note
Test text is limited to 100,000 characters and at most 5,000 matches are listed. Patterns with nested quantifiers such as (a+)+$ can still be slow (catastrophic backtracking) — if the page freezes, simplify the pattern.