Passkeys are a standardized form of passwordless authentication that use a combination of a browser API and an authentication device like your phone or computer to offer secure, site-specific credentials. They are built on top of industry standards such as WebAuthn and the Client to Authenticator Protocol (CTAP), which makes them a reliable form of secure authentication. Passkeys use public key cryptography to generate an authentication key pair, with public keys stored on a backend server and private keys stored on the device where they were generated. The two main categories of passkeys are synced passkeys, which backup private keys to a passkey manager like Apple iCloud Keychain or Google Password Manager, and device-bound passkeys, which use private keys that never leave the originating device. Passkeys offer unique security benefits such as being phishing-resistant, reducing hacking targets, and offering cross-device authentication. They also provide intuitive usability benefits such as being fast and compatible with different ecosystems. However, their adoption is currently limited due to a lack of widespread implementation and support for alternative forms of authentication. Implementing passkeys requires verifying with the Twilio Passkeys server-side tools, which will provide the necessary integration for passwordless consumer authentication.