Last December, Apple gave its registered developers an important heads-up about a new rule requiring that all new apps and app updates for iPhone, including universal ones, be built with the iOS 12 SDK and support the new iPhone XS Max form factor.
Today, the company warned developers that all new and updated iPhone software submitted to App Store on and after March 27, 2019 must be built with at least the iOS 12.1 SDK and support the new 2,688×1,242 pixel resolution on the latest iPhone XS Max model.
This means that any apps built against the latest SDK will run in fullscreen display mode on the latest devices, taking full advantage of all the pixels.
App Store screenshots for these devices will also be required.
Furthermore, all new and updated apps for iPad, or universal apps, must be optimized for the native display resolution of the latest 12.9-inch iPad Pro model, which has the highest resolution of any iOS device at 2,732×2,048 pixels.
Apple explains that apps which take full advantage of adaptive UI layouts and safe area insets should look great on iPhone XS Max with minimal effort on the developer’s part.The new requirements are meant to prevent the proliferation of unoptimized apps that on larger-screened iPhones like the Max appear blown up with fuzzy text/images and black borders.
Apple also requires that all new apps and updates submitted to watchOS App Store on or after March 27 be built with the watchOS 5.1 SDK or later and support Series 4 watches.
Thanks to its bigger display with rounded corners, Series 4 can display more information, but apps must be optimized to take full advantage of the increased pixel count.
Last but not least, Apple wrote this to clarify the changes in memory accounting:
iOS 12 and tvOS 12 require apps to use memory far more efficiently than before. If you have difficulty reducing your app’s memory requirements, contact us to request an entitlement for your app to use iOS 11-style memory accounting.
iOS 12 is now running on more than 80 percent of devices worldwide.