Two-factor or two-step authentication for logging in to any online service is an extra safety step taken to ensure that the rightful user of an account personally approves a sign-in using their phone apart from entering their credentials on a login screen. Until now, Facebook needed the user’s mobile phone number to achieve the second step in authentication. It would send a one-time password through SMS to the user and expect the user to enter the same to verify their identity.
Now, however, Facebook, is allowing its users to use third-party authentication apps like Google Authenticator and Duo Security to sign in securely without asking them for their mobile phone numbers. Google Authenticator is a software token that implements two-factor authentication using the Time-based One-time Password algorithm to verify sign-ins. It’s available as an app on Google Play Store for Android phones and on App Store for iOS devices. Google Authenticator has been around for the last seven years now and has eased the process of two-factor authentication during sign-ins for online services like Google and Dropbox.