Various app developers have told Tech Crunch that Apple is starting to reject apps that use 'cookie tracking' technology. The technology is also referred to as 'HTML5 first party cookies' or 'Safari flip-flop'.
These solutions are being used as an alternative to UDID. Apple told developers in 2011 that it planned to block the ability of iOS apps to access the UDID in order to satisfy lawmakers who have put iOS under scrutiny. Apple then started rejecting apps that used UDID last year, and following that move developers started seeking alternatives. At the time we wrote that UDID alternatives were being sought.
UDID's reputation wasn't aided by news last year that UDID information had been leaked. At one point it was thought that iPhone UDIDs had been given to the FBI, but this was later found to be untrue. Instead the UDIDs had been stolen from a digital publishing firm.
Apple recently introduced an Advertising Identifier in iOS 6.1. This new tracking technology, called IFA or IDFA (Identifier for Advertisers), doesn't identify you personally. It just provides data that advertisers can use to send relevant ads to the right devices.
There is general agreement that IFA is an improvement over the previous system of Unique Device Identifiers (UDID).
Fiksu's Craig Palli suggested to TechCrunch that Apple likely wants developers to start transitioning to its own Ad Identifier technology.