Password Strength Checker
Check how strong a password is, entirely offline.
🔒 Runs entirely in your browser — your password is never sent anywhere, not even to this site's own server.
Estimated entropy: bits
- At least 8 characters
- Contains an uppercase letter
- Contains a lowercase letter
- Contains a digit
- Contains a symbol
- Not a commonly used password
How Password Strength Checker works
How does the password strength checker work?
It checks your password against six criteria - minimum 8 characters, and the presence of lowercase, uppercase, digit, and symbol characters, plus a check against a list of about 30 common leaked passwords. From the character types present it calculates a character pool size, then estimates entropy as length × log2(pool size) in bits, and maps that entropy to a five-level label from "Very weak" to "Very strong."
When would I use this?
It's a quick way to sanity-check a new password before you commit to it, whether you're setting up an account or updating one that was flagged as weak. The live checklist makes it obvious which specific requirement - length, a missing symbol, and so on - is dragging your score down.
Does the password ever leave my browser?
No - the entire check runs client-side in JavaScript, comparing your input against a hardcoded common-password list and computing entropy locally, with nothing transmitted to the server. Keep in mind the entropy estimate is a simple mathematical approximation based on character-set size, not a full password-cracking model, so it can rate a predictable but varied-looking password more favorably than it deserves.