Meanwhile Google Play headed in the opposite direction, growing 30 percent to over 3.6 million apps. Appfigures reckons App Store's decline is the result of Apple's tougher enforcement of review guidelines and its clean-out of apps that weren't updated to support 64-bit architecture.
Apple in 2016 told developers it planned to scour the App Store for apps that no longer function or meet the current review guidelines.
And, as TechCrunch notes, last year's big clean-out targeted clones and spam apps as well as template-based apps which, together with the 64-bit requirement, resulted in a significant number of removed apps.
However, Apple's restrictions and removals aren't the only reasons the App Store shrank for the first time since 2008. Appfigures says new app submissions also dropped 29 percent, with developers releasing 755,000 new apps over the year. By comparison, Android developers released 1.5 million new apps, marking a 17 percent rise on 2016 submissions.
The other driver of app store growth is the quantity of apps that are ported from one platform to the other. Again, there were twice as many apps ported from iOS to Android than the other way round.
According to Appfigures, there are now about 450,000 apps that are on both iOS and Android, representing about 8.5 percent of all apps.
The most popular non-native developer tools for Android and iOS apps were Cordova and Unity, followed distantly by Adobe Air, Cocos2D, Xamarin, Appcelerator, Corona, and React Native.
However, apps developed with non-native tools only accounted for 24 percent of iOS apps and 10 percent of Android apps, down from 2016 when 32 percent of iOS apps and 27 percent of Android apps were built non-natively.
The US is by far the largest source of apps, accounting for 33 percent of them, while 15.9 percent are from China. The rate of apps coming from China is also on the rise, numbering just over 100,000 in 2015 but rising to 250,000 new apps in 2017.
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