From time to time Apple updates the requirements for submitting applications to the App Store. Apple has done so again. Starting tomorrow, March 27th, 2019, all new application submissions, as well as app updates, will have some new requirements.
Any app submission will need to be built against the iOS 12.1 SDK, or newer. As part of this requirement, new submissions will require screenshots for the iPhone XS as well as the iPad Pro, if the app is universal.
If you develop watchOS apps, there are also new requirements as well. All watchOS updates will need to be built against the watchOS 5.1 SDK as well as supporting the Apple Watch Series 4.
There is one last item to be aware of, regarding your apps. iOS 12 has changed the way that the amount of memory your app uses. Under iOS 11, if your app used purgeable, nonvolatile memory, the resources you allocated were not counted against your application’s memory usage. This changed in iOS 12. Now, all of the memory that your app allocates will count against its limit. And if your app exceeds the limit, it will likely be terminated.
Many applications already meet these requirements, but if your application does not, it is something to be cognizant of, and you will have to meet the requirements, otherwise your application will be rejected.