Apple Trims App Fat with iOS 9

While iOS 9 features a number of key improvements, there’s one addition all Apple users will love. Beginning with iOS 9, 3 features under the App Thinningwill work to reduce storage requirements for iOS apps. These storage space use reductions come on top of the already reduced footprint of iOS 9 and it’s relatively small OTA update.

The first and the biggest addition is App Slicing. Right now, each iOS binary downloaded contains all the assets for the various compatible devices. With App Slicing, the app store will only allow the necessary parts be downloaded. So iPhone 6 Plus won’t download 32bit code and 2x assets while the iPhone 5C won’t download 3x assets and 64bit code. Cutting out nearly half the resources in some cases will make installing and updating apps a much quicker and less data intensive operation.

The next feature is On-Demand Resources. Just like the name implies, resources can be tagged by the developer as not necessary at install and only downloaded as needed. After the user is done with the assets, they can be removed again. For instance, apps with in-app purchases won’t download those assets until the user has bought it and tutorials can be removed once played. Game levels or assets will only be downloaded once the user is near to obtaining them and maybe even removed once the user clears the level. The executable code will not be able to be marked as ODR, but images and media files can. It’s not known how ODR handles the lack of an internet connection right now.

Bitcode is the final feature and is related to App Slicing. Instead of submitting pre-compiled binaries, developers hand in an “intermediate representation” of their app. This allows the App Store to compile the app based on the installing device, improving performance and reducing app size. It also means that Apple can make its own compiler tweaks at install, as well as strip out the unnecessary code, enabling App Slicing. This is not unlike Android’s ART or Dalvik which compiles the app either at install or runtime though Android has yet to remove unnecessary assets.

With all of these space saving addition, 8GB iTouch and iPhone 4S users will be sure to be able to stop juggling their storage. Even users with 16GB of space will stand to benefit hugely from reduced app sizes. It’s possible to always remove pictures and media after their taken but having to uninstall and install apps can be more of a pain. While not perfect, this is one answer to the lack of expandable storage with Apple devices. Maybe Google can take a cue this time around and start trimming down Android app sizes as my Nexus is starting to get full.