Earlier quoted context omitted.
If I'm on someone else's computer and I want to use a passkey on my phone, the computer will display a QR code. I scan the QR code with my phone, the phone signs the login request and posts it to the service's callback. Then I'm logged in on that new device. If my phone's camera is broken but both devices have bluetooth, it can do the handshake over bluetooth. If I'm on someone else's computer and I want to use a pas…
This is good in theory but in practice doesn't always work. It isn't just a QR code like I would like it to be, its a QR code and you need bluetooth. Maybe there is a hypothetical world where bluetooth drivers actually work on windows machines and can connect to a mobile device seamlessly but that is not my experience. Across multiple windows machines i often have a problem where windows just decides the machine does…
in poland we have similar to passkey implementation for government profile, that is then used to login to most/all government websites or to sign government documents. you point the camera on the qrcode, confirm it on the phone and you are done. this same app has your ID, which can be used in most places (shops, banks, police etc).
and btw im using linux (main box), macos, android and ios - no issues so far with really cross device usage