Apple developers just got an important notice from the company: beginning April 1, it will require all iPhone/universal apps to natively support the iPhone X’s Super Retina display, all new iOS apps to be built with iOS 11 SDK or later, and new Apple Watch apps to be built with watchOS 4 SDK or later. Apple has issued similar notices in the past to developers regarding requirements, such as for larger iPhone screen sizes. This latest prerequisite comes six months after the debut of the iPhone X.

VentureBeat reports that, “Apple’s push for Super Retina display support could be taken either as obvious or as suggestive of future development trends.” Although the new Apple requirements are no surprise, “some may take the requirement as a hint that more Super Retina devices — or similarly proportioned iPhones — are coming later this year.”

Not all apps will be treated alike. Those already in the App Store can continue to be built with “some older versions of the iOS and watchOS SDKs, but Apple said today that it will stop accepting apps built with the watchOS 1 SDK on April 1.” VentureBeat says that, “roughly 65 percent of iOS devices are currently running iOS 11, 28 percent are on iOS 10, and 7 percent are on earlier versions of iOS.”

Operating system breakdown numbers are not available for the watchOS. Pushing developers to adopt the newer operating system is not simply for its inherent improvements, but also for better security and “under-the-hood enhancements.”

In the past, Apple mandated that, for example, “new apps include 64-bit support after the release of iOS 8 and comply with a new ‘flat’ visual style after the debut of iOS 7,” which was the beginning of “widespread changes across its devices.” Not every change triggers a mandate, however: “more than two years after its release, Apple has not imposed a similar screen support requirement for the 12.9-inch iPad Pro,” most likely because it “didn’t represent any major directional shift for iPads or other Apple products.”