I'm building an app which is very similiar to venmo: it allows users to text money to eachother.

While it is not per se necessary to know the phone number of the user that is registering, it could make sense to ask for it. Since it's an app in which money can be spent, it could also be 'sold' as an extra security feature.

Should I ask users for their phone number?

  • Would you give your phone-number to a website / app if it wasn't required?
    – JonW
    Jul 4, 2014 at 23:31
  • I would if it would make sense to. It allows users to transfer money to their friends and sms is the channel to aquire users, more whatsapp style. It is not required to make the app function, but I could make it required for the user.
    – bdv
    Jul 4, 2014 at 23:34
  • 2
    The more fields you have - especially those asking for personal, identifying information - the fewer people will register. Why not just ask for phone numbers at the point of use that the user actually needs to enter it.
    – JonW
    Jul 4, 2014 at 23:37
  • altough i'm not sure if it's a feature we'll implement, but we could use phone numbers to check who of the user's friends are on the service in a later stage, but entering your phone number does not provide any additional features for the user, so it would make more sense to do it in the setup than anywhere else imo.
    – bdv
    Jul 4, 2014 at 23:41
  • 1
    That sounds like it makes less sense to ask for it than not, to be honest. "We won't use your phone number details yet, and might not ever, but give it to us now anyway". Don't think about it from your business perspective and how useful it may be to have that data in future, think about it from the end user point of view who has a form to fill in.
    – JonW
    Jul 4, 2014 at 23:55

3 Answers 3


Only ask for a phone number if having it provides additional capability.

For example, if you implement a process to text a confirmation code to the number, you could show a "Number Verified" badge next to those users.

TradeMe (New Zealand's dominant online auction site) does a similar thing with "Address Verified" - it's optional, but gives other users more confidence the account.

If you're not doing something like this right now, don't ask for the phone number now.

Instead, ask for it when you launch the feature, if you do.


It seems like the answer's in the question. Asking users to do something for no reason might sound good in a meeting, but in UX terms it's wholly bad. This is a kind of UX tone-deafness I used to see a lot in local government; it comes from thinking of your users as a component of your internal processes, rather than people you're trying to engage with.

Also, deliberately misrepresenting your purposes could come back to haunt you: don't say "it's for security" if you're not using it for security.

If you ever come up with a specific reason to capture the information, you can just ask for it at that time; and then, you'll be able to tell your users the truth about why you want it, and why they want to give it to you.


should I ask for a phone number anything even though it is not required?

No. If it's not required, it's not required. Why burden the user with entering data that is not needed?

If you need it later, then wait and ask later. Don't add hurdles where you don't need them.

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