Regex-Tester

A real-time regex playground in your browser

Build and debug regular expressions interactively. As you type the pattern, the test string is re-evaluated and matches are highlighted instantly. Capture groups (both numbered and named) show up in a side panel with their values for every match. No round-trip to a server, no signup, nothing tracked.

Nativer JavaScript-Regex-Typ

We use the browser's own RegExp engine, which means the patterns you test here will behave exactly the same in your JavaScript code. Modern features are all supported: lookbehind (?<=...), named groups (?<name>...), Unicode property escapes \p{...}, and the s (dotall) flag.

Ersetzen-Modus

Toggle replace mode to preview a regex-based substitution. The replacement supports all the standard $ tokens: $1, $2 for numbered groups, $<name> for named groups, $& for the full match, $` for text before the match, $' for text after, and $$ for a literal dollar sign.

ReDoS-Schutz

Catastrophic backtracking — patterns like (a+)+$ on long input — can hang any regex engine. We have two safety nets:

• Hard timeout: if matching takes longer than 2 seconds, we abort and tell you.
• Match cap: a maximum of 10,000 matches per evaluation. Beyond that we stop and mark "10000+" so the UI stays responsive.

Datenschutz

Your patterns and test text never leave the page. The engine is built into your browser. No external library is loaded, no analytics fires when you type, no requests go out.

Häufige Anwendungsfälle

• Validate email, URL, phone or postal-code patterns.
• Extract structured data from logs or scraped text.
• Build search-and-replace queries before running them in your editor.
• Debug a regex that "should work but doesn't" — the highlight makes the problem visible immediately.
• Learn regex by experimentation with the cheatsheet at the bottom.