Passkeys were suggested two years ago. Nowadays, the technology is more mature. Passkey portability is being worked on.
Passkeys should be an extra option for logging in.
When properly implemented, like on Fastmail and Google, the 'Log in with Passkey' prompt automatically appears when you visit the login page, but only if you have a passkey set up. This is very powerful, as this would make logging in insanely fast, for the people that have passkey set up.
Another advantage: it's phishing-proof. The passkey simply won't work on other websites.
I attached an image of how Fastmail has implemented it. The login page detects that I have a Passkey set up, and I only have to authenticate by laying my finger on the fingerprint scanner, and in a fraction of a second I'm logged in. Note that I don't have to enter my e-mail address, even.
