What’s a YubiKey? A YubiKey is basically a tiny device that plugs into your USB slot and pretends to be a keyboard. When you tap the little golden disc, it types out a One Time Password (OTP). Through the Yubico API, you can easily validate this password, and use it in combination with another method of authentication (such as a password or ssh key) to achieve two-factor authentication (2FA). Many popular websites like Google, Facebook, and Github allow you to enable 2FA via YubiKeys.