Regex Editor & Tester

Matches whole words consisting only of the digits 0 and 1, provided they don't start with a digit followed by two identical digits. The negative lookahead (?!(\d)(\d)\1) uses a backreference to reject tokens whose second and third characters repeat, such as 011, 100, 000, or 111. Useful in exercises demonstrating lookahead assertions, backreferences, and word boundaries for filtering binary-like tokens (e.g., alternating 0s and 1s) in text.