Regex Editor & Tester

Validates a string of 1-20 characters that must contain at least one digit, one lowercase letter, and one uppercase letter. A negative lookahead rejects any string containing common special characters such as !@#$%^&*()[]{}~|\/?><.,:;' and backtick. Typically used for password or username validation where alphanumeric-style input with mixed case and digits is required.