The distinction
A synced passkey is stored by a compatible passkey provider and can become available on other devices after the provider's own sign-in and unlock process. A passkey held only on a particular hardware security key or device may require that physical device for use. The account's website may show several passkey entries, each with a different origin.
A loss scenario
If you lose a phone holding your only device-bound credential, you need another registered passkey or a supported recovery route. If a passkey was synchronized by your provider, access on a replacement device depends on recovering that provider account and satisfying its security checks. Neither route is instant if your phone was your only verification method.
Make the setup resilient
Record the provider or hardware source of important passkeys and keep a second independent sign-in method. Google's
passkey overview describes provider synchronization and nearby-phone sign-in; its
account help describes trying another way after device loss. A passkey is phishing-resistant at sign-in, but losing every recovery route can still lock you out.
