What is phone Auth?

Phone-based authentication involves sending a one-time password (OTP) to a user over a separate communication channel (e.g. SMS, MMS, WhatsApp, Facebook Messenger, Viber or even voice) from the IP channel (internet) used by the application, providing security in case the IP channel is compromised.

You can use Firebase Authentication to sign in a user by sending an SMS message to the user’s phone . The user signs in using a one-time code contained in the SMS message.

Phone authentication allows users to sign in to Firebase using their phone as the authenticator . An SMS message is sent to the user (using the provided phone number) containing a unique code. Once the code has been authorized, the user is able to sign into Firebase.