Test a regular expression against some text and see exactly what it matches.

JavaScript regex tester. Highlights all matches in the test string, shows capture group values, and displays match index, length, and input position. Supports all JS regex flags (g, i, m, s, u, y, d).

Evaluates regex via the JavaScript RegExp engine (V8/SpiderMonkey). Displays global match array from matchAll() with full match, capture groups, named capture groups, and indices (flag d). Flag d (hasIndices) supported in Chrome 90+/Firefox 88+. Performance guard: regex with catastrophic backtracking potential flagged via a timeout mechanism (100ms execution limit).