Double opt-in confirmation link or confirmation code?

Question

I read everything about double opt-in on this site and I saw on Sign up: Double opt-in still best practice? What about mobile? answers someone speaking about sending a confirmation code instead of a confirmation link by email. It works like that :

1. User fills in form and enter an email address
2. As soon as the email address is validate, a confirm code is sent to the user's email, requiring him to fill this code in the form in order to validate it.
3. the user comes back to the form and fills the code. Once he clicks done on the form, he is registered and double opted-in by anticipation.

As a UX designer, I really don't like the idea of being forced to validate a process while having a crucial information given in another tool. I really much prefer providing a link to confirm a form registration. What do you think?

Answer 1

Both are valid, which is why both are in practice.

However, when it comes to the question of mobile, sending a code may work best, the reason being that in order to access the internet on a mobile, you will likely be using a smartphone or similar relatively sophisticated device.

When you are sent a message on such a device one of two things typically happens- the message is overlayed on the screen, or a summary of it is placed on a screen overlay accessible on top of the currently viewed browser page (e.g. swiping down from the top of the screen on an android phone), in both cases as long as the code is one of the first items in the message, the user doesnt have to leave the current page or the browser application, they can simply view the message summary, get the code and type it into the current page.

Link validation requries leaving the browser, going into an email app, then clicking/tapping the link to load up the browser often in a new tab, leaving the original open. This is a significantly less fluid workflow.

That said, this does depend on a few if's and but's, you could always send a code and a link.