Regex for Password Strength Validation
Quick Answer: A common password strength regex uses lookaheads: ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$. This requires 8+ characters with at least one uppercase, lowercase, digit, and special character. Modern guidance (NIST SP 800-63B) recommends length over complexity.
FAQ
Is requiring special characters in passwords good security?
NIST guidelines (SP 800-63B) recommend minimum 8-character length and checking against breach databases. Complexity rules (uppercase, special chars) are no longer recommended as they lead to predictable patterns.
How do regex lookaheads work for password validation?
(?=.*[A-Z]) is a lookahead that asserts "somewhere in the string there is an uppercase letter" without consuming characters. Multiple lookaheads at position 0 check independent requirements.