On-demand resources are app resources that are hosted on the App Store and are separate from the related app bundle that users download. They enable smaller app bundles, faster downloads, and richer app content. At runtime, the app requests sets of on-demand resources, and the operating system manages downloading and storage. The app uses the resources and then releases the request. After downloading, the resources may stay on the device through multiple launch cycles, making access even faster.
Note that if you export your app for testing or distribution outside of the App Store, you must host the on-demand resources yourself. Also, executable on-demand resources are not supported.
On-demand resources are available for iOS and tvOS apps.