Regex Tester

Regex Tester

The Regex Tester lets you build and debug JavaScript regular expressions against real text with live feedback. Matches are highlighted as you type, with capture groups, positions and a full match list, so you can iterate quickly without a console.

Why use Regex Tester

  • Live highlighting of every match in your test string.
  • Capture groups, named groups and exact match positions.
  • Toggle all flags — g, i, m, s, u, y — and see the effect instantly.
  • Clear, immediate errors for invalid patterns.

How to use Regex Tester

  1. 1Enter a pattern. Type your regular expression in the pattern field (no slashes needed).
  2. 2Add a test string. Paste the text to match against; matches highlight live.
  3. 3Tune flags. Toggle g/i/m/s/u/y and review the matches, groups and positions below.

Frequently asked questions

Which regex flavour is this?
JavaScript (ECMAScript) regular expressions, the same engine your browser and Node.js use.
What do the flags mean?
g = global, i = case-insensitive, m = multiline, s = dotall, u = unicode, y = sticky. Toggle them to change matching behaviour.
Are capture groups supported?
Yes — each match lists its numbered capture groups and positions, including named groups.

Developer notes

This uses the JavaScript (ECMAScript) regex engine, so behaviour matches your browser and Node.js exactly — including Unicode property escapes under the u flag and sticky matching under y.

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