Regular Expression Tester

Pattern + flags + test string → live matches, groups and highlighting.

Quick answer: Free regex tester: test JavaScript regular expressions with live match highlighting and capture groups. Cheat-sheet included. Runs in your browser.

Pattern

Flags

Test string

–Matches found

Quick cheat sheet

\d digit • \w word char • \s whitespace • . any char • + one or more • * zero or more • ? optional • [abc] set • (a|b) or • ^ start • $ end • {2,4} quantifier

How to use

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About this tool

Regular expressions (regex) find patterns in text — emails, phones, log lines, code. This tester runs your pattern against a test string with live highlighting and shows capture groups per match. Flags control behaviour: g (all matches), i (case-insensitive), m (multiline anchors). Start with \d+ (digits) or \w+@\w+\.\w+ (simple email) from the cheat sheet.

FAQ

Which regex flavor is used?

JavaScript (ECMAScript) — the same engine as Node and browsers.

Why does my match loop forever?

Zero-length matches are guarded automatically; also avoid patterns like a* without /g limits.

What are capture groups?

Parentheses () capture parts of a match — listed per match below the highlighter.

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The complete regex tester guide

Prefer the long version — a worked example, the mistakes people actually make, and answers to real questions? The blog guide Regex Tester — Complete Guide, Mistakes & FAQ covers all of it step by step.

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Regular Expression Tester

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