Regex Tester & Validator
Test, validate and match regular expressions
Test, validate and match regular expressions
Matches credit card numbers for American Express (starting with 34/37), Visa (4), MasterCard (51-55, 65), and Discover (6011, 65). Includes checks to reject numbers with repeated digits, sequential patterns, or known invalid test numbers like 424242. Uses PCRE lookarounds to ensure the number is a standalone token, not embedded in a larger digit string. Suitable for validating card input in forms or detecting card numbers in text.