What is the difference between enabling two-factor authentication via SMS or an authentication app?

You have two options when it comes to 2FA: SMS or an authentication app. If you choose SMS, your 2FA verification code will be sent to your phone via SMS when you attempt to sign into SeatGeek. If you choose to use an authentication app, you will need to download an authentication app that supports time-based one-time passwords (TOTP), such as Google Authenticator or Authy. An app will allow you to scan a QR code to set up 2FA, and then will show a new verification code whenever you open the app.