Create random passwords in your browser. Nothing is sent or stored.
No. Passwords are generated in your browser and never leave your device. Nothing is saved, so copy the one you want.
They use your browser's built-in cryptographic random number generator, the same kind used for security features.
Use at least 14 characters for ordinary accounts and 20 or more for important ones like email and banking. Longer is stronger.
It estimates entropy in bits from the length and character types you choose. Above about 80 bits is very strong for online accounts.