IconVault's Breach Check tells you whether your password has appeared in a known data breach, using the HaveIBeenPwned password database. It uses k-anonymity: your password is hashed with SHA-1 in your browser and only the first 5 characters of the hash ever leave your device, so the full password is never sent anywhere. You get a clear answer: clean, or breached with a count of how many times it was seen.

It is free, needs no signup, and the password field is never stored or logged. The honest note: a clean result means the password has not shown up in known breaches, not that it is strong. If a password is breached, change it everywhere you reused it, and consider a password manager plus two-factor authentication going forward.