FIDO (Fast Identity Online) Authentication is a set of open technical specifications that define user authentication mechanisms that reduce the reliance on passwords.
FIDO protocols are designed from the ground up to protect user privacy. The protocols do not disclose sensitive user data that can be used by different online services to collaborate and track a user across the services. Other sensitive data like biometric fingerprints and PINs never leaves the user’s device to ensure it cannot be intercepted or compromised by an attacker.
To authenticate a user, an application – often referred to as the relying party – uses FIDO-specified client-side APIs to interact with a user’s registered authenticator. For web applications, client-side APIs include WebAuthn implemented by the web browser, which in turn calls on FIDO CTAP to access the authenticator.