Regex Tester
Test a regular expression live, with capture groups and replacements.
Everything here runs entirely in your browser. Nothing you type, paste, or upload is ever sent to a server, logged, or stored.
About the Regex Tester
Runs a regular expression against sample text as you type, highlighting every match, listing the capture groups, and previewing a replacement so you can see the result before committing to it.
When you would use it
- Building a pattern and checking it against real examples.
- Working out why a pattern matches something it should not.
- Testing a find-and-replace before running it on real data.
What it does not tell you
This uses the browser's own regular expression engine, and the dialects differ. A pattern that works here may behave differently in Python, PCRE, Go or a database, particularly around lookbehind, named groups and Unicode. Be careful with patterns containing nested repetition: on some inputs those can take effectively forever to run, in this page and in production alike.