Apple has announced that app slicing, a feature that came to iOS 9 as part of app thinning, is now once again available to developers. The feature had originally been affected by an iCloud backup issue, which has since been resolved.
The issue affecting app slicing has been fixed, and device-specific versions of apps will be delivered when downloaded by users running iOS 9.0.2 or later.
Apps with support for app slicing can be downloaded in pieces by users. Rather than downloading all data for an application, you'll download just the pieces you need for your device. So new iPhones, with 64-bit processors and Retina displays, won't download assets meant for non-Retina devices with 32-bit processors if the app supports it.
For more on app slicing, as well as app thinning as a whole, be sure to read our handy explainer.