Participating in the program meant users were able to check out features before the official release - something only those with paid developer accounts had access to in the past - in return for submitting feedback. The program continued throughout the rest of the year, allowing users to test iOS 9.2 and eventually iOS 10. Last year, Apple introduced a public beta program for iOS users who were willing to help the company test iOS 9. IOS 9 public beta profile on an iPhone 6S.
