Regex Tester
Test a regular expression against sample text in your browser.
Tool workspace
Browser flags: g i m s u y
Tests a regex locally. Pattern max 200 chars; sample text max 50,000 chars; matches capped at 100 (ReDoS guard).
How it works
Enter a pattern, optional flags, and sample text. Matches and capture groups are listed locally.
ReDoS guards: pattern max 200 characters, text max 50,000 characters, matches capped at 100. Empty pattern with empty text clears the result—no error.
Browser flags: g i m s u y. PHP Domain tests use PCRE flag letters.
ReDoS guards: pattern max 200 characters, text max 50,000 characters, matches capped at 100. Empty pattern with empty text clears the result—no error.
Browser flags: g i m s u y. PHP Domain tests use PCRE flag letters.
Examples
- Pattern \d+ against abc123 → Match 1: "123"
- Invalid pattern → clear error message
Privacy
Privacy: this tool processes patterns and text locally in your browser. We do not log or store what you paste. Login is not required.
FAQ
Is my text uploaded?
No. Regex testing runs entirely in your browser.
Why are there length limits?
Limits reduce ReDoS risk from pathological patterns on large inputs.
Do I need an account?
No. All published tools work for guests without login.