A hardware-backed passkey is a cryptographic login credential that is stored or protected inside dedicated hardware, such as a security key or a trusted device module. Instead of relying on a shared password, it uses public-key cryptography: the private key stays on the device, and the service verifies a signed challenge during sign-in.
This matters because hardware-backed passkeys are much harder to phish, replay, or steal with malware than passwords or one-time codes. Attackers cannot simply trick a user into typing a secret into a fake page, because the credential is bound to the real device and the real site. Defenders use them to strengthen access to sensitive systems, especially admin portals, cloud consoles, and cyber-focused services. They also raise operational requirements: organizations need enrollment, backup, and lost-device recovery processes that are as strong as the login control itself.