One of the features of iOS 9 is App Thinning. For those hearing about this for the first time, basically the concept behind App Thinning to help keep app sizes smaller, thus allowing users with 16GB iOS devices to free up more space on their phones. However due to an iCloud bug, the feature was delayed.
Thankfully it looks like the bug has been fixed as Apple has recently confirmed that app slicing (a part of App Thinning) is now back into play. According to the Apple developer page, “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.” Users interested in learning more can hit up Apple’s website for the more technical details.
So what does this mean for the end user? Basically this means that your apps only download the necessary assets and components related to your phone. This means if you have an iPhone 6s, only the assets needed for the app to operate on the iPhone 6s will be downloaded, skipping all the unnecessary files for the iPad, older iPhones, and so on.
This should dramatically reduce file sizes especially when you consider that a lot of image files, especially for games, can get pretty big for the iPad, so downloading the app on your phone should result in smaller files and more storage for you at the end of the day.