Lean Mobile App Development

Phone number sign-up - a great alternative

WhatsApp and a couple of other apps are using the phone number of the device to identify a user for the registration. This is done through an SMS verification code. The user enters his phone number and receives an SMS with a verification code, which he needs to type into the app. This will ensure that the phone number is correct. There are even some implementations that intercept the receiving of the SMS verification code and then fill in the code automatically. This will take away another step from the onboarding flow:

You have to make it clear to the user that his phone number is used for verification ...