Regex Lab
This regex tester is created by Jonathan R Reed to make quick pattern checks less painful. Test, visualize, and share regular expressions with live matches, replacements, and shareable URLs. Everything runs client-side.
Use Regex Lab when you need to debug a pattern before it goes into an API route, validation rule, parser, log filter, or data cleanup script. Live matches make it easier to catch greedy groups, missing anchors, accidental case sensitivity, and replacement output that looks correct until it touches real text.
Practical regex debugging
A useful regular expression helper should make the input, pattern, matches, and replacement result visible at the same time. That is the fastest way to see whether a pattern is matching the intended text or only passing on a small happy-path sample.
The tool is built for short implementation checks: validating a slug, extracting IDs from logs, cleaning copied data, checking a route matcher, or confirming a replacement before it is moved into code. Because the workspace runs in the browser, sample text and patterns do not need to be sent to a remote formatter.