Enter the pattern
Type your regex and choose flags.
Code & Data Tool
Regex Tester
Test regex patterns, inspect groups, preview replacements, and avoid browser freezes.
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About this tool
What is Regex Tester?
Regex Tester lets you try a regular expression against sample text, inspect capture groups and preview replacements. It has a timeout to stop catastrophic patterns freezing your browser.
Useful when you need to
- Build a pattern for a form field
- Check which parts of text match
- Test a replace before using it in code
How to use
How to use Regex Tester
01 02 Add test text
Paste sample text.
03 Read matches
See matches and groups.
04 Try a replacement
Preview a replace string if needed.
Tips
Get better results
- Test with both text that should match and text that should not.
- Nested repetition can be slow, which is why the timeout exists.
FAQ
Frequently asked questions
Why did it time out?
The pattern may backtrack heavily. Simplify it.
Is it private?
Yes.
Which regex flavour?
JavaScript regular expressions.
More practical guides · File handling and privacy · Report an incorrect instruction