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Regex Tester

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Test a JavaScript regular expression against any text — matches highlight live, and every match lists its numbered and named capture groups. Uses your browser's native regex engine, not a separate flavor to translate mentally.

How it works

  1. Type your pattern and flags
  2. Paste or type test text — matches highlight instantly
  3. Every match and its capture groups are listed below

Frequently asked questions

Which regex flavor does this use?

JavaScript's native RegExp — the same engine your browser and Node.js use, so what you test here behaves the same in your code.

Is my regex or test text sent anywhere?

No — matching runs entirely in your browser via the native RegExp engine.

Can I see capture groups?

Yes — every match and its numbered/named capture groups are listed below the highlighted text.

#RegexTester#JavascriptRegexTesterOnline#RegexTesterNoServer#RegexMatchGroupsHighlight

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From the blog

regex101 makes you pick from seven regex flavors. Your browser only runs one.
dev

regex101 makes you pick from seven regex flavors. Your browser only runs one.

PCRE2, Python, Go, Java, .NET, Rust, POSIX — regex101 supports all of them, which is powerful and also a question most web developers don't need to answer.

2026-08-30

Update history

  • 2026-08-30 Added: a cover image (magnifying glass over highlighted text with regex delimiter marks) — used as the card thumbnail, social share image, and blog title image.
  • 2026-08-30 Launched: live JavaScript regex tester (no button) — highlights matches in the test text, lists every match with numbered/named capture groups, entirely client-side.