Weak Password Checker

About Weak Password Checker

Password strength meters built into signup forms are often shallow, checking only for length and a mix of character types without catching the patterns real attackers actually exploit — common leaked passwords, keyboard sequences, and repeated characters that dramatically weaken a password even when it technically satisfies every complexity rule.

This tool checks a password against several real weaknesses at once: raw entropy (based on length and character variety), whether it matches one of the most commonly leaked passwords ever recorded, whether it contains a keyboard or alphabetic sequence (like "qwerty" or "abc"), and whether it has three or more repeated characters in a row — all well-documented patterns that make a password meaningfully easier to guess.

The entropy calculation estimates how many possible passwords could exist given the password's length and which character types it uses — a rough but genuinely informative measure of brute-force resistance. A password can have decent raw entropy and still score poorly here if it matches a known-leaked password or contains an obvious pattern, since real attackers try those first, long before resorting to true brute force.

This is useful for checking a new password before committing to it, understanding specifically why a password is considered weak (not just that it is), improving password habits, and building intuition for what actually makes a password hard to crack versus what merely satisfies an arbitrary complexity rule.

How it works

1. Type a password. Checked entirely in your browser as you type — nothing is sent anywhere.
2. See the strength meter and score. From very weak to very strong, with the estimated entropy in bits.
3. Review specific issues. Concrete reasons the password is weaker than it could be.