We had originally planned to go all-in on passkeys for ONCE/Campfire, and we built the early authentication system entirely around that. It was not a simple setup! Handling passkeys properly is surprisingly complicated on the backend, but we got it done. Unfortunately, the user experience kinda sucked, so we ended up ripping it all out...
Bitwarden stores your passkeys on your local device. It can sync the passkey between devices but that’s end to end encrypted, bitwarden never has access to any of your passkeys or even your passwords.