//g
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Nothing is uploaded. Just open it and start.

Test and debug regular expressions, without leaving your browser

Enter a pattern and sample text, and watch matches highlight live with full capture-group details. No sign-up, no watermarks, nothing between you and your data.

Live match highlighting

See every match highlighted in your sample text as you type, updating instantly.

Capture groups & details

Inspect numbered and named capture groups for every match, plus its exact position.

Common regex flags

Toggle g, i, m, s, u, and y and watch matches update immediately.

100% private, 100% client-side

Your pattern and text never leave your browser. There's no server round trip, ever.

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Frequently asked questions

Which regex flavor does this use?
JavaScript's built-in RegExp engine (ECMAScript). Most syntax — character classes, quantifiers, groups, lookahead/lookbehind — is shared with Python, Java, and other languages, but a few things aren't identical (Python's (?P<name>) named-group syntax vs JavaScript's (?<name>), for example), so double-check edge cases against your target language.
Why does my pattern only find one match?
Turn on the "g" (global) flag. Without it, the regex engine stops after the first match — which is exactly what this tool shows you, mirroring real JavaScript behavior.
Is my pattern or sample text sent to a server?
No. Matching runs entirely in your browser using the native RegExp engine. Nothing is uploaded, logged, or stored anywhere.
What do the highlighted matches mean?
Every match your pattern finds is highlighted in the sample text. Click a highlighted match, or its card in the match list, to see it picked out and inspect its numbered and named capture groups.
What happens if my pattern is invalid?
The error straight from the regex engine's parser is shown immediately — things like an unterminated group or a bad escape sequence — so you can fix the syntax without guessing.
Is the Regex Tester really free?
Completely free. No login, no credit card, no time-limited trial, and no premium tier gating anything. Live highlighting, capture-group details and the common flags are all included, with no pattern or sample-text limits. One small ad slot covers the hosting bill, and that's the whole business model.
Do I need an account to use it?
No — nothing to register for, nothing to download, and no email address asked for at any point. Type a pattern and some sample text, and matches highlight immediately.