Regex Tester
Test JavaScript patterns and inspect matches, offsets, and capture groups.
Runs locally with a 1.5-second timeout. Enter a pattern without surrounding slashes.
Flags: g all matches · i ignore case · m multiline · s dot matches newlines · u Unicode · y sticky. Offsets use UTF-16 code units.
About Regex Tester
Run regular expressions in a separate browser worker. A slow pattern is terminated after 1.5 seconds, keeping the page responsive. Results include matched text, capture groups and named groups, with null for unmatched groups. Test text and patterns stay in your browser.
Frequently Asked Questions
Your browser’s JavaScript RegExp syntax. Use the g flag for all matches; without g or y only the first match is shown. Some newer flags may require a recent browser.
Patterns: 2,000 characters. Test text: 100,000 characters. Results: up to 500 matches and 100,000 characters of match data. Each worker is terminated after 1.5 seconds. Offsets count UTF-16 code units, as JavaScript does.