Password Strength Analyser gives a rough measure of guessing difficulty: the size of the character pool, the length, and penalties for repeats, keyboard runs, digit-only strings, and very common passwords.
It runs in your browser and nothing you type is sent or stored. The result is a guide. A high score is not a promise that a password is safe.
It assumes an attacker who has the hashed password and can try about ten billion guesses per second against a fast hash. That is a deliberately pessimistic setup.
Length matters more than variety. A short password with symbols has fewer combinations than a long one without. The tool also penalises patterns like runs and repeats.
No. It is a smaller model with a short built-in list of common passwords. It will not catch every dictionary word or personal detail, so treat borderline results with caution.
No. The check is entirely local and the field is cleared when you leave the page.