Phone & OTP Authentication in React Native with Firebase

In this video, I explain how to implement Firebase Phone Authentication inside an Expo React Native app. You’ll learn how to configure test numbers in Firebase, use libraries for international phone inputs and OTP fields, and handle real-world cases on iOS and Android devices (including SIM-based auto verification). I also cover system design insights, production pitfalls, and why I’m moving towards BetterAuth for more control. 00:00 - Intro & overview of phone authentication 01:00 - Setting up phone auth route in Expo Router 03:00 - Adding phone input & OTP input libraries 05:30 - Creating phone number input with country codes 08:00 - Authentication flow explained (OTP wait vs email flow) 10:00 - Handling confirmation & OTP validation 12:00 - Enabling phone provider in Firebase console & test numbers 15:00 - Controlled inputs & validation before sending OTP 17:00 - Confirming OTP & showing user UID after authentication 20:00 - Real device behavior (SIM card auto verification in Android) 24:00 - Handling auth state changes for production reliability 27:00 - Adding SHA keys for debug, release & Play Store builds 29:00 - System design comparison: Firebase vs BetterAuth for phone auth 32:00 - Moving towards self-hosted auth with Twilio + BetterAuth 33:00 - Wrap up & conclusion You can email me at for further queries: [email protected] If you want to have a consulting session about Expo React Native or to develop Web/App/AI for your business,schedule it here so we can have a meet in Google Meet or a Zoom Call: https://cal.com/gautham-vijayan/30min You can find the source codes for all of my videos in topmate: https://topmate.io/gautham If you have any other questions, please leave it in the comments or contact me via Twitter (X) over DM's. Here is my Twitter (X) profile: https://x.com/gautham_vijay_ #ReactNative #Expo #FirebaseAuth #PhoneAuthentication #OTPLogin #MobileSecurity #BetterAuth