OnSubmitSteps
- Enter a regex pattern.
- Set JavaScript flags such as g or i.
- Paste sample text.
- Review matches and replacement output.
Development · free tool
Regex tester for JavaScript patterns, matches and replacements
Test JavaScript regular expressions, flags, matches and replacements.
Input and result
Use it well
How to use Regex Tester
Common use cases
- Form validation
- Check patterns for emails, IDs, slugs or user input.
- Text extraction
- Extract repeated patterns from logs or copied text.
- Replacement testing
- Preview cleanup rules before using them in code.
FAQ
Frequently asked questions
Which regex flavor is used?
The tester uses JavaScript regular expressions, so behavior follows the browser RegExp engine.
Why can a regex be slow?
Some nested quantifiers can cause expensive backtracking. Simplify risky patterns before using them on large text.
Can I test replacements?
Yes. Enter replacement text to preview the transformed output.
Are my inputs sent to a server?
OnSubmit tools run in the browser whenever the task can be processed locally. Avoid pasting production secrets, real banking details or personal data into public tools.