Regex Tester
Tests a regular expression against sample text, showing matches, capture groups and flags.
Input
Output
Enter a pattern.
Runs entirely in your browser. Your input is not uploaded or stored.
How to use this calculator
- Enter a regex pattern, flags and some test text.
- See every match, its position and any capture groups.
How it works
Runs your pattern with the JavaScript regex engine and lists all matches and groups. Invalid patterns show a clear error.
Worked example
\d+ on 'a12 b3'. Matches '12' and '3'.
Tips
- Runs entirely in your browser. Your input is not uploaded or stored.
Frequently asked questions
Which flavour?
JavaScript regular expressions (the same engine the browser uses).
Privacy?
Runs entirely in your browser. Your input is not uploaded or stored.
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Cite this tool
Zerdly. (2026). Regex Tester. Retrieved from https://www.zerdly.com/tools/regex-tester/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.