App thinning is an optimization that lets developers tailoring app delivery to the capabilities of the user’s particular device, with minimal footprint. This means that if you have an iPhone, you won't have to download all the resources necessary for the app to run on an iPad.
Although app thinning was supposed to go live with iOS 9, Apple disabled the feature due to a bug. Hopefully, the issue will be resolved soon. We'll keep you up to date.
What's New In This Version:
Xcode 7.0.1 fixes bugs related to app thinning.
Xcode 7 includes Swift 2 and SDKs for iOS 9, watchOS 2, and OS X 10.11 El Capitan.
You can download Xcode from the App Store for free.