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Note: This has to do with App Slicing and App Thinning that was introduced by Apple in late 2015. Nothing to do with your 2012 question.

https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/AppDistributionGuide/AppThinning/AppThinning.html

http://www.imore.com/app-thinning-ios-9-explained

http://www.macrumors.com/2015/10/05/ios-9-app-slicing-now-available/

http://www.appcoda.com/app-thinning/

Given that my iOS storage has been running out of space, I try to keep iOS App versions which are smaller in size and not update unless essential or compelled to {e.g. Uber compels updates}

So, I recently did a comparative analysis for 2 apps and what sizes (in MB) they show in 3 places (iTunes 12.3.3 On Windows 8.1 x 64):

App Names:
Todoist 11.0.3
Wunderlist 3.4.3


Current Latest Versions updated & synced this weekend:

iTunes > AppStore | As shown on AppStore before download
70
95

iTunes > My Apps | As shown in iTunes after download
34
53

iPad 2 - iOS 9.0.2 > | As seen under iTunes > Sync > App Selection area after Install/ Sync
65
87

iPhone 5 - iOS 9.0.2 > | As seen under iTunes > Sync > App Selection area after Install/ Sync
XX
YY
{Will post these numbers soon as well}

I cannot understand why the "complete un-thinned App from the AppStore would take more space when thinned for the iPad or iPhone"


  • Possible duplicate of How much free space do I need to install an app update? – Andrew Larsson Apr 11 '16 at 16:10
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    Things have changed with recent iOS releases and application thinning, so I don't think it's a duplicate as such (answers might be different this time round). – nohillside Apr 11 '16 at 17:51
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    @AndrewLarsson - This has to do with App Slicing and App Thinning that was introduced in late 2015. Nothing to do with your 2012 question. – Alex S Apr 12 '16 at 9:42
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I can see multiple reasons for that happening:

A) Compression

Apps are downloaded in compressed form from the app store. It is similar to a Zip-file. When the app is installed on the phone, it is uncompressed by the app installer software on the phone.

B) Differential updates

If you already have the app installed, and are merely downloading an update for the app - you could be downloading a differential instead of the full app. For newer iOS versions, the App Store will calculate the difference between what you already have and the new version of the app, enabling you to download less. However it will still take up the full amount of space on the disk after the upgrade has taken place.

C) App downloads after first use

When you use an app for the first time, many apps will download extra data that is stored with the app on your phone. This could account for differences in app size as listed by the App Store, compared to the amount of space the app takes on your phone in practice.

  • @jk - I like the direction you are going but it needs more detailed info/ math. Is Itunes now doing Differential downloads between app releases? I dont think so. I have yet to see a single app download partial updates.. Every update has mean double digit MB downloads. – Alex S Apr 12 '16 at 9:49
  • They claim to be doing so. See Apple Technical Q&A QA1779 where they write: "When generating the update package, the app store compares one or more prior versions of your app to the new version and creates an optimized package for each that contains only the content that has changed between versions of your app, excluding any content that did not change". Some call this "delta app updates". – jksoegaard Apr 12 '16 at 15:39
  • Your claim about block sizes is incorrect. Using statfs() on both my rMBP 15" (running OS X 10.11.4) and iPhone 6S (running iOS 9.3.1), the block size for the root filesystem on both is 4096 bytes. – Dennis Munsie Apr 13 '16 at 16:12
  • I wasn't able to check on iOS right now, but you're right regarding OS X. I checked using "diskutil info", but I got the device and allocation block sizes mixed up. The allocation block size is indeed 4 kB on OS X, whereas it is the irrelevant device block size which is 512 bytes. – jksoegaard Apr 13 '16 at 18:36

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