Crypto
Regex Tester
Test regular expressions. Real-time matches, capture groups, replace. JavaScript engine.
How to use
- Enter a domain, URL, or value relevant to Regex Tester.
- Run the check and review the output carefully.
- Apply recommended fixes, then run the check again to verify.
Common use cases
- Pre-deployment validation for Regex Tester.
- Incident triage when security checks fail in production.
- Periodic security review as part of technical SEO and hardening.
Example inputs
[a-z]+\d{3}-\d{4}(?<name>\w+)Common issues and fixes
Unescaped special chars
[ ] ( ) { } * + ? . \ need escaping in regex. Use \ before them.
Catastrophic backtracking
Nested quantifiers like (a+)+ can freeze on long input. Simplify pattern.
Wrong regex engine
JavaScript regex differs from PCRE. No lookbehind in old browsers. Test here.
Recommended remediation
Escape [ ] ( ) { } * + ? . \ in literal mode. Use g for global, i for case-insensitive. Test with edge cases.
FAQ
Is Regex Tester free to use?
Yes. This tool is free and can be used without account registration.
Do you store submitted values?
Only the minimum processing needed for the check. For client-side tools, data stays in your browser.
How should I use these results?
Use the output as a diagnostic baseline, apply fixes in your stack, then re-run the check to confirm remediation.