Passkeys are built on the FIDO2 standard (CTAP2 + WebAuthn standards). They remove the shared secret, stop phishing at the source, and make credential-stuffing useless.
But adoption is still low, and interoperability between Apple, Google, and Microsoft isn’t seamless.
I broke down how passkeys work, their strengths, and what’s still missing
Most of the sites I’ve seen use it as the single auth source. That said, using multiple forms of authentication in a layered model only improves security.