Apple is moving developers towards adopting the company's own iOS 6 tracking technology and not their homegrown methods. One of these alternative techniques is cookie tracking and, according to a report in TechCrunch, Apple may be rejecting apps that use this method.
To understand how we got to the point where Apple is rejecting apps that use tracking cookies, we need to take a step back to iOS 5 and earlier. In previous versions of iOS, developers used a device's UDID to track users. The UDID is a 40-character unique identifier assigned to each iOS device that developers used to track game progress, check subscription status and monitor ads. Apple phased out UDID tracking in iOS 5 and added support in iOS 6 for its own tracking methods, advertisingID and identifierForVendor.
Some apps are circumventing these approved APIs by using tracking cookies that work on mobile devices almost like they do on the desktop. Craig Palli, VP of Business Development at mobile app marketing firm Fiksu, explained to TechCrunch that, "Within local storage, an app developer can drop a token -- an ID, if you will -- and then retrieve it later. In this regard, it works like a cookie, so the industry frequently uses it and talks about it like it's a cookie."
Palli claims the number of apps being rejected for using this tracking method has increased over the past few weeks. He hypothesizes that Apple is gently nudging developers towards its own tracking technology. You can read more about this form of tracking and Apple's app rejection in the TechCrunch article.