Hi jpalu,

That's a great question, but not necessarily an easy one to fix.

What are the criteria you want to use for "a fast/slow mobile"?
MetaMod has easy access to some mobile detection but that is not necessarily the same thing as determining if the mobile is going to be suitable to display your ads.

You could switch based on detecting Android and iPhone browsers (plus desktop, TVs, tablets and bots), if you are confident that any Android or iPhone would be capable of displaying the ads. But there's no easy way to determine the CPU speed of the mobile device. At least this method would prevent the ads from being shown on old "feature phones".

Do you think that would be effective in your case?

Cheers,
Stephen