Want to secure your online accounts with two-factor authentication (2FA)? Then you’ll need an authenticator app to scan the relevant QR codes during the setup process. Such an app can also generate the TOTPs (Time-Based One-Time Passwords) that you need, in addition to your login passwords, to unlock your 2FA-enabled accounts. You can either go for web-based authenticator apps or choose from one of the free 2FA Mac apps we cover below. 1.