How secure is UUID? Is it possible to fake it?

[bottasergio]

Is UUID reliable? I have to verify that device is allowed to use some services from my server. Can I trust that UUID sent from my app is real or is it any way to fake it? Is it possible that 2 o more devices have the same UUID?

[kashban]

It is not anymore. Apple changed the UUID API with iOS 7 in a way apps will only get a fake UUID, not the real one. Same goes for the MAC Address.

There is a vendor Id you can use to identify your App on a device as long as it is not removed and reinstalled. That's the best Apple has to offer to iOS Developers.