Regex Tester & Debugger
Test and debug regular expressions in real time with visual match highlighting, capture group extraction, and replacement substitution.
Capture Groups & Match Positions
100% Local Browser Privacy
All computation happens right in your browser's JavaScript engine. No data is ever sent to any remote server.
Instant Results
Zero network latency. Calculations and formatting are executed instantly with high cryptographic and mathematical precision.
Works Offline
Once loaded, this tool can function completely offline with no active internet connection required.
Frequently Asked Questions
Which regex engine does this use?
It uses ECMAScript (JavaScript) standard regular expressions natively supported in all modern web browsers.
How do capture groups work in substitutions?
Use $1, $2, etc., in the replacement pattern to insert the corresponding captured groups.