PSA | Legacy 32-bit iOS apps will fail to run on iOS 11
iOS 11 is all set to hit compatible Apple devices and now is a good time to ensure that all your installed apps are compatible with the latest OS. Starting from iOS 11, Apple allows running only 64-bit apps. The OS update itself is only available for devices that sport 64-bit chips such as the Apple A7 SoC or higher, starting with the iPhone 5S. Legacy apps that are still 32-bit need to be updated by the developer before you can use them. The update will not, however, uninstall incompatible apps automatically.
Apple started warning users from iOS 10.3 onwards about the imminent transition to 64-bit. In iOS 11, users who try to launch 32-bit apps will be greeted with a message that the app needs to be updated. It's a good idea to check app compatibility before updating to iOS 11 just to ensure that all currently installed apps will work fine. You can check apps that are not compatible with the new update by going to Settings > General > About > Applications. Any apps that show up in the list cannot be launched after updating the device to iOS 11.
Although many popular apps have made the transition to 64-bit, some classic apps still linger on to 32-bit code (Flappy Bird, anyone?). If you rely on any of the 200,000-odd legacy apps that are still on the iTunes Store, you should probably hold off updating your device. However, it is still not clear whether these apps would be eventually removed from the iTunes Store by Apple.
iOS is not the only harbinger of change in the Apple ecosystem, though. Starting January 2018, even the Mac App Store will start accepting only 64-bit apps with macOS High Sierra being the last OS update to fully support 32-bit applications. Although change can sometimes be disruptive, this development does make some sense from Apple's perspective. For one, the company need not maintain two independent libraries for 32-bit and 64-bit apps. It also forces developers to embrace modern standards and better streamline their code. Although the percentage of impacted apps is on the lower side, ultimately, it is up to the app developers to make their apps compliant with Apple's latest and greatest.