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Regex tester — offline

JavaScript regular expressions with live highlighting and capture groups. Your sample data never leaves the page.

100% private — files never leave your device
//g
Test text

How it works

  1. 1

    Type a pattern and pick flags.

  2. 2

    Paste sample text — matches highlight live.

  3. 3

    Inspect capture groups per match below.

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Frequently asked questions

Is my test data sent to a server?

No — the pattern runs with your browser's own JavaScript RegExp engine, right on this page. Log excerpts and sample data stay on your machine.

Which regex flavor is this?

JavaScript (ECMAScript) — including named groups, lookbehind, and the u flag. Patterns may behave slightly differently in PCRE or Python.

Why does a complex pattern freeze briefly?

Catastrophic backtracking is a property of the pattern itself. If a pattern hangs here it would hang in your code too — which is useful to know before shipping it.