The most recent beta of iTunes reportedly won’t allow iPhone and iPad owners to reinstall an older iOS version. This is apparently the result of a bug rather than a change of policy by Apple.
It seems Apple will continue to allow users to downgrade to a previous version if a serious problem is found in a new one.
A change in iTunes 220.127.116.11 to prevent people from installing older iOS versions was first noted and confirmed on Reddit.
Cult of Mac reached out to Apple asking if the change was deliberate or a bug. We were informed that Apple hasn’t changed its policy on iOS downgrades.
iOS Downgrades 101
Moving to a previous iOS version requires installing an IPSW file on the mobile device. These come from Apple, and are only available for recent versions of iOS. So, for example, it’s currently possible to downgrade from iOS 12.1.3 to version 12.1.2 or 12.1.1 but not anything earlier.
Moving the IPSW onto the iPhone or iPad requires iTunes. Installing a previous iOS iteration instead of the newest one has always been an option, but that’s not possible in the most recent iTunes 18.104.22.168 beta. Those who want the option to downgrade their iOS devices in the future should avoid installing this pre-release version.
Note: This article was updated with significant new information at 3:45 pm PT.