How it works
The password is picked using your browser’s secure random number generator, the same source used for encryption keys, not a simple random function.
Each type of character you tick appears at least once. Longer is stronger: each extra character multiplies the number of possible passwords.
The strength figure is bits of randomness. About 70 bits is strong for most accounts and 100 or more is very strong.
Good to know
Use a different password for every account, and store them in a password manager rather than in your head.
Turn on two-step verification for important accounts such as email and banking.
Some sites reject certain symbols. If so, untick symbols and make the password longer instead.
Frequently asked questions
Is it safe to generate passwords on a website?
This one runs entirely in your browser. The page makes no request containing your password, and nothing is stored. You can check this by disconnecting from the internet and using it.
How long should a password be?
At least 12 characters for ordinary accounts, and 16 or more for email, banking and your password manager.
Why avoid look-alike characters?
Letters such as I, l and O look like the numbers 1 and 0. Avoiding them helps if you must read the password aloud or type it from paper.