Regex Tester
Write a regular expression and watch every match highlight live in your test text, with flags and capture groups visible.
How to use the Regex Tester
- Enter your regular expression and any flags.
- Paste the text you want to test against.
- Review the highlighted matches and captured groups.
About the Regex Tester
Regular expressions are far easier to build incrementally than to write correctly in one attempt, which is why immediate visual feedback matters so much. Start with a literal string, then generalise one piece at a time and watch the highlighting change. This uses the JavaScript regex engine, so the syntax matches what you will get in browser and Node code — some patterns from PCRE or Python will behave differently.
Frequently asked questions
Which regex flavour is used?
JavaScript's engine, so the behaviour matches what you get in browser and Node code.
What do the flags mean?
g matches all occurrences rather than stopping at the first, i ignores case, and m makes ^ and $ match at line boundaries.
Why does my pattern match nothing?
Common causes are unescaped special characters like . ( ) [ ] and a missing global flag when you expect multiple matches.
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Runs entirely in your browser — nothing you enter is uploaded. Last reviewed and updated .