How strength is measured
Every character is drawn with the browser's cryptographically secure random generator (with rejection sampling, so no character is more likely than another), and at least one character from each selected set is guaranteed. Strength is estimated as entropy: length × log₂(pool size). Around 60 bits is reasonable, 80+ bits is strong for anything important.
The best password is one you never type or remember: use a password manager, and use a unique password for every account.
Passwords are generated on this page and deliberately never saved anywhere — not even in this browser. Only your option settings are remembered.