6 months ago I analyzed the version 66.0 of the Facebook.app for iOS: https://blog.timac.org/2016/1018-analysis-of-the-facebook-app-for-ios

The version 66.0 was a 165 MB app on an iPad Air 2 (64-bit). It was a monolithic app with its main binary being more than 100 MB.

The version 87.0 is now available: 253 MB on the same iPad Air 2 with only 64-bit code. In just 6 months, the Facebook.app size grew by 88 MB!

Download Info

Let’s see what changed…

App content

Looking at the app content of the version 87.0 using GrandPerspective gives a good overview:

Facebook 87.0 content

Here is how the content of the version 66.0 looked like: Facebook 66.0 content

As you can see, the Facebook.app has been completely restructured:

  • the main binary is now only 19 MB
  • there is a huge 136 MB framework FBSharedFramework
  • there is another 26 MB framework called FBNotOnStartupPathFramework

Duplicated resources

One of the reason the app size grew is due to multiple copies of the same resources inside the app.

unetshallow_init.pb

You can actually see in the previous screenshot 3 copies of the same file unetshallow_init.pb:

  • Facebook.app/Frameworks/FBNotOnStartupPathFramework.framework/opticalflow_resource/unetshallow_init.pb
  • Facebook.app/Frameworks/FBSharedFramework.framework/opticalflow_resource/unetshallow_init.pb
  • Facebook.app/opticalflow_resource/unetshallow_init.pb

unetshallow_init

Keeping only one copy would save 7.2 MB.

DataFiles

Similarly the DataFiles folder appears 3 times. Keeping a single copy would save around 2 MB:

  • Facebook.app/DataFiles/
  • Facebook.app/Frameworks/FBNotOnStartupPathFramework.framework/DataFiles/
  • Facebook.app/Frameworks/FBSharedFramework.framework/DataFiles/

DataFiles

FBFacecastTipJarResources

Some resources called FBFacecastTipJarResources appear to be duplicated no less than 6 times in the app! The FBFacecastTipJarResources resources only take 150 KB on disk but 6 times makes 900 KB.

One example:

  • Facebook.app/FBFacecastTipJarResources/sent.m4a
  • Facebook.app/Frameworks/FBNotOnStartupPathFramework.framework/FBFacecastTipJarResources/sent.m4a
  • Facebook.app/Frameworks/FBNotOnStartupPathFramework.framework/sent.m4a
  • Facebook.app/Frameworks/FBSharedFramework.framework/FBFacecastTipJarResources/sent.m4a
  • Facebook.app/Frameworks/FBSharedFramework.framework/sent.m4a
  • Facebook.app/sent.m4a

Other duplicated resources

There are a bunch of other duplicated resources, amongst them:

  • modelMetaData.bin: 4 x 1 MB
  • schemaMetaData.bin: 4 x 830 KB
  • FBCommunicationSoundKit.bundle: 3 x 741 KB
  • MNSounds.bundle: 3 x 528 KB
  • FBSoundControllerResources: 3 x 500 KB
  • RelaySchema.json: 3 x 319 KB
  • libPhoneNumber.bundle: 3 x 172 KB
  • CACerts.plist: 3 x 168 KB
  • FBFacecastBroadcastKitResources: 3 x 98 KB
  • Montserrat-SemiBold.ttf: 3 x 70 KB
  • ReactMobileConfigMetadata.json: 3 x 33 KB
  • FBEntityCardsModuleResources: 3 x 33 KB
  • add-photo@2x.jpg: 3 x 29 KB
  • FBFacecastWithKitResources: 3 x 20 KB
  • FBNativeArticleEngagementActionsResources: 3 x 20 KB
  • FBFeedbackReactionsKitResources: 3 x 12 KB

These listed resources count for 15.5 MB. By removing the duplicated resources, you could save at least 10 MB.

Duplicated images

The Facebook.app contains 3 assets.car files:

  • Facebook.app/Assets.car: 11.3 MB for 2267 items
  • Facebook.app/Frameworks/FBNotOnStartupPathFramework.framework/Assets.car: 10.3 MB for 2126 items
  • Facebook.app/Frameworks/FBSharedFramework.framework/Assets.car: 9.5 MB for 1972 items

assets

All the 1972 images in FBSharedFramework are inside the main Assets.car and also part of the FBNotOnStartupPathFramework Assets.car. So there are 3 times the same 1972 images taking 3 x 9.5 MB = 28.5 MB.

Keeping a single set of these 1972 images would save 19 MB.

The remaining images in the main Assets.car (2267 - 1972 = 295) and in the FBNotOnStartupPathFramework Assets.car (2126 - 1972 = 154) are unique.

New localizations

The Facebook.app gained 5 new localizations, increasing the app size by 4.2 MB:

  • hi.lproj (1.3 MB)
  • hr.lproj (692 KB)
  • hu.lproj (750 KB)
  • ro.lproj (709 KB)
  • sk.lproj (713 KB)

Also each localization got a new 12 KB file called AdsCountriesConfig.json. This adds 336 KB.

DO_NOT_USE_OR_YOU_WILL_BE_FIRED

When analyzing the version 66.0 I completely missed some amusing Objective-C interfaces, protocols and methods:

@protocol FBDeprecatedAppModule_DO_NOT_USE_OR_YOU_WILL_BE_FIRED

@protocol FBLoginFacilitatingAppModule

@interface FBTimelineModule : FBNativeAppModule_DO_NOT_USE_OR_YOU_WILL_BE_FIRED

@interface FBNotificationsModule : FBNativeAppModule_DO_NOT_USE_OR_YOU_WILL_BE_FIRED

@interface FBProductionLockoutModule : FBNativeAppModule_DO_NOT_USE_OR_YOU_WILL_BE_FIRED

@interface FBSearchModule : FBNativeAppModule_DO_NOT_USE_OR_YOU_WILL_BE_FIRED

__RODATA segment

Although the main binary is much smaller than the App Review limitation, the Facebook.app still uses a __RODATA segment containing sections generally found inside the __TEXT segment. For more information about it, please look at the previous post https://blog.timac.org/2016/1018-analysis-of-the-facebook-app-for-ios.

Conclusion

Between version 66.0 and 87.0, the Facebook.app has been completely restructured. The main -and only- binary has been split in several frameworks.

It appears however that during this process a couple of resources have been unnecessarily duplicated:

  • opticalflow_resource: 3 x 3.6 MB
  • DataFiles: 3 x 1 MB
  • images: 3 x 9.5 MB
  • FBFacecastTipJarResources: 750 KB
  • Other duplicated resources: 15.5 MB

Removing the duplicated resources would save at least 40 MB. This partially explains why the app size has increased by 90 MB.

Update 15.04.2017: Facebook.app for iOS [v. 88.0] cleans up duplicates