When is the Scan Credit Card option available on iOS8 Safari?

Question

So Safari offers Scan Credit Card feature on iOS8 with some credit card forms.

My question is, how does Safari determine when to offer this option?<

Answer 1

This is now all broken after upgrading to iOS 8.1.3 this morning. When on iOS 8.1.2 all of the above worked just fine - now the keyboard option to scan credit card simply does not appear. Here's my code, which did work yesterday on iOS 8.1.2 and does not work today on iOS 8.1.3:

Credit Card Number 1




Expiry month 
 



Expiry year