Web Authentication API: Resident Keys

Security keys are generally stateless save for a global signature counter. While it’s technically possible to implement a stateful security key, physical tokens generally encrypt their state in a credential ID that is stored on the server of the relying party. Resident keys allow the security key to keep state and thus allow a username-less login experience by just proving a local PIN to the device. Developers can exercise this via the existing Webauthn standard.