Upcoming AppTrackingTransparency requirements
April 20, 2021
With the upcoming public release of iOS 14.5, iPadOS 14.5, and tvOS 14.5, all apps must use the AppTrackingTransparency framework to request the user’s permission to track them or to access their device's advertising identifier. Unless you receive permission from the user to enable tracking, the device's advertising identifier value will be all zeros and you may not track them.
When submitting your app for review, any other form of tracking — for example, by name or email address — must be declared in the product page’s App Store Privacy Information section and be performed only if permission is granted through AppTrackingTransparency. You'll also need to include a purpose string in the system prompt to explain why you'd like to track the user, per App Store Review Guideline 5.1.2(i). These requirements apply to all apps starting April 26, 2021.
As a reminder, collecting device and usage data with the intent of deriving a unique representation of a user, or fingerprinting, continues to be a violation of the Apple Developer Program License Agreement.