“App thinning,” a new feature Apple was set to introduce to iOS 9 that would make apps and games much smaller, is on hold due to an iCloud bug.
App thinning lets iOS, tvOS, and watchOS developers “create apps that use the most device features, occupy minimum disk space, and accommodate future updates that can be applied by Apple,” explains a support guide in Apple’s developer center.
In a nutshell, app thinning allows developers to strip away certain assets from their apps that may not be required on all devices, thereby saving valuable storage space.
If you have an older iPhone, for instance, you won’t need to download assets created specifically for the larger displays of the iPhone 6 and 6 Plus, and the new iPhone 6s and 6s Plus. You can also do without code specifically for Metal, which isn’t available on older devices.
App thinning could make huge improvements to your user experience if you have an older iPhone or iPad that has only 16GB of storage. But unfortunately, it was not made available with iOS 9 as originally planned thanks to an iCloud bug.
“App slicing is currently unavailable for iOS 9 apps due to an issue affecting iCloud backups created from iOS 9 where some apps from the App Store would only restore to the same model of iOS device,” Apple explains.
This bug meant that when you restored an iPhone 5s backup on an iPhone 6s after upgrading, it would restore only the assets required for the iPhone 5s. Until Apple solves this problem, app thinning is on hold.
Apple insists, however, that app thinning will be added in the future, but there’s no timeline for it just yet.