Password Strength Checker
Entropy-based password analysis with real-time feedback. We never store or transmit your password.
How Password Entropy Works
Entropy (measured in bits) represents how many guesses an attacker would need on average. A password with 60+ bits of entropy is considered strong for most purposes. We calculate it aslength × log₂(charset_size). A 12-character password mixing all character types achieves ~78 bits — effectively uncrackable by brute force.
Scans for dictionary words, names, common passwords, dates, keyboard walks (qwerty), and repeated sequences
Accounts for common substitutions (@ for a, 3 for e), capitalization patterns, and leet speak
Assigns a guess count — the number of guesses an attacker would need in the worst case
Guess count converted to time at multiple attack speeds: online throttled, online unthrottled, offline slow/fast hash
0=too guessable, 1=very guessable, 2=somewhat guessable, 3=safely unguessable, 4=very unguessable
Spec: zxcvbn (Dropbox, 2012) — realistic attack modeling, not character-class rules