Passwordless Sign In with a FIDO2-enabled security key such as a YubiKey in conjunction with Microsoft Entra ID (Azure AD) provides high security while maintaining ease of use. There is no longer any need to enter a username and password. For users with private mobile devices who do not want to install the Microsoft Authenticator app, a security key from YubiKey offers a good alternative. This tutorial sets up a YubiKey 5 security key for passwordless sign in to Microsoft Azure and Microsoft 365 services.