When you wanted to pay, you selected to pay with your internet bank, selected the bank, and got transfered to a bank login page, you logged on with your phone app or hardware token, and was taken straight to a page where you authorized that specific transaction, you authorized it with your phone app or hardware token and it was done!
No need to use card numbers, no need to register, it just worked.
Then Klarna killed it.
Other services still offer that, but they are few and far between
In Poland this kind of authentication is a widespread standard and a default option pretty much. Generated tokens all around, payment apps tied to hardware etc.. No logins necessary, only pins or other forms of a password if the transfer amount goes above a set threshold.
The bank auth is still with a token here in Sweden, but Klarna changed their system to no longer accept individual transaction approval, to a system where I would need to grant them access to automatically withdraw money from my accounts up to three days after making a purschase online. This is obviously a way to save mobey as they can bundle up several transactions into one and only need to pay a transaction fee once.
A few years after this happened I discovered that I could generate a temporary card number in my banks online portal, brilliant, that went away a year or so after I discovered it as they redesigned the online banking portal.
I need to get a new account with a different bank card, I just haven't had time to bother with that yet. Though it would have saved me plenty of grief on a company trip to spain where I lost my bank card just before the trip...
All the way back in the early 2000s my bank offered a service where you could generate onetime card numbers with a specific dollar value tied to them. It disappeared around 2008. I wonder why?