A website requires users to validate their email – it's how the user receives their password creation link, and email is essential to several core workflows.

There is now also a need to collect and validate SMS numbers, though two factor authentication is only needed for a specific high-level task that not all users will need.

My sense is that we should make the mobile number optional in the registration flow (per this answer) and let the user validate it later, when it's truly needed. However, in the moment when it's needed (let's say, right before publishing a page on the site), a "Please validate your phone number" message will be very disruptive and break the user's flow, especially if there are problems.

What might be the best solution?

  1. Validate both phone and email for everyone in registration, and never make the user think about it again. It just seems like a lot of validation for a user who might be ready to create an account, but might not yet be very engaged with our site.
  2. Validate the email in registration, and the phone in the "moment of need", but try to make the process as smooth and unobtrusive as possible.
  3. Validate the email in registration, and the phone number later, but before the user gets to the "moment of need", perhaps when they start editing the page they're going to publish.

Or, is there a better process for this?

3 Answers 3


Maybe this is a variation of another answers, just a kind of clarification of option 3.

You may introduce the concept of status (role, etc.) of user and clearly mention it in user interface. Say after registration with email verification user become Reader. And you promote in your interface that to write post user need to become Writer. So user constantly have ability to learn what he need to do to become Writer - describe phone verification procedure after clicking 'Whant to become Writer?' and/or 'Become Writer!' blocks.

  • I'm marking this as the answer because I think that asking for validation at the moment the role becomes granted by an administrator is the right approach.
    – Izquierdo
    Commented Jul 7, 2021 at 20:10

Just offer the option. Let the user know that these steps will be required at some point, but let them choose whether to do them at the time of registration or at a later time. You'll find that those who are already "sold" on the service will likely complete the entire registration process at once.

On the other hand, those who just want to cheque it out will probably refrain from providing all of their information until they are quite sure they will use the service.

This is a very common mechanism in many companies to understand user indecision, and it is usually reinforced with mails to let the user know why they should use the service.

Bottom line is that you need to understand (through research) is the user's intentionality. Once you understand the goals and pain points of your user experience, the process becomes clearer, even if you have to offer divergent paths or user journeys


To advocate for the user: please don't make me enter my phone number if I don't need to.

Just recently I signed up at a certain real estate search website that asked for my phone number without explanation. Sure enough, the marketing calls and texts began coming in a couple days later. I was so mad.

Do as Amazon and Google do. Let them make an account without entering a phone number. Then give them an option to add one later, both at an arbitrary time and whenever they try to use the feature that requires it. Validate at that point.

If you want a little more of a push, still following Amazon and Google's lead, you can prompt them randomly on sign-in. "Have you thought about adding a phone number?" Just make sure the UI doesn't suggest it's a required step to continue.

But to answer your question more directly: there's not much point saving potentially invalid numbers. If you were to ask for it optionally at registration, you would want to validate it (if entered) at that point. Otherwise, you need to validate before use anyway, and asking for it on registration and asking for validation later is just double friction.

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