64-bit Day of Reckoning

Apple announced late last year that all updates submitted the iOS App Store would need to include 64-bit support starting on June 1st. New apps have been required to include a 64-bit slice since February.

Now that the day has come and gone, I thought it would be interesting to look at the architectures included in the top 100 free apps in the US store. Are most apps holding out as long as possible, or have they all jumped on the 64-bit train? The full data behind this post can be found here.

As you might expect, all of the top apps include an armv7 slice for compatibility all the way back to the iPhone 3GS. Over half are now including arm64 slices, and just 4 include the short-lived armv7s architecture.

Xcode’s default build setting for architectures has evolved through recent versions. In Xcode 5.1, they aggressively included armv7, armv7s, and arm64. Starting with Xcode 6, the default has backed off to a more reasonable combination of armv7 and arm64. This is largely reflected in the architecture breakdown of the top apps. It’s interesting to note that the only 2 apps including all 3 slices are made by Apple (Find My iPhone and iTunesU).

Why Not Include all the Architectures?

Adding an additional slice to an app’s binary can significantly increase the size of the application package. The binary is often the largest file in the package, and it compresses poorly because it is encrypted prior to distribution on the App Store. Back in December, I tweeted about the massive size of Facebook.app’s binary.

With the addition of arm64, the uncompressed size of Facebook’s binary is now over 115 MB! I’m guessing they wish they didn’t have to ship that slice.

Apple suggests targeting fewer architectures in Technical Q&A 1795: Reducing the size of my App. With the new requirement for including 64-bit support, targeting armv7 and arm64 will be the best configuration for most apps. Perhaps iOS 9 will come with smarter App Store distribution, so that users only have to download the slice needed for their device’s CPU. Add that to my WWDC wish list!