Password Strength
& Breach Checker

This tool performs all strength analysis entirely in your browser — nothing is transmitted. For the breach check, it uses k-anonymity: your password is converted to a SHA-1 hash, and only the first 5 characters of that hash are sent to HaveIBeenPwned. This makes it mathematically impossible to reverse-engineer your password from what is transmitted.

Length and unpredictability matter most. A 16-character password of random characters is vastly stronger than an 8-character one using every character type. Common patterns — keyboard sequences, word-number combos, date formats — are among the first things attackers try. The strongest passwords are long, random, and unique to each service.

It means that exact password was included in a data breach and indexed by HaveIBeenPwned. Attackers use these databases before attempting brute-force — they try every known breached password first. A password found in breach data should be considered compromised and replaced on every service where it is used.

The most effective approach is a passphrase — four or more random, unrelated words joined together. "correct-horse-battery-staple" is stronger than "P@ssw0rd1!" because length and randomness matter more than complexity. For most accounts, the better solution is a password manager so you only need to remember one strong passphrase.

A strong password protects against brute-force attacks. However, on platforms like Google Drive, Dropbox, and iCloud, the provider holds your encryption keys — meaning your files can be accessed by the provider, law enforcement, or through a provider breach regardless of password strength. Client-side encryption protects your files even if your account is compromised.