Originally, iOS apps were 32-bit only. Then, as you may recall, Apple iOS began supporting 64-bit apps starting with the iPhone 5s, eventually requiring all new apps submitted to the App Store starting on 2.1.2015 to include 64-bit support.
In order to prepare users for 64-bit only support, starting in iOS 10.3 Apple began notifying users who opened 32-bit apps that when they upgrade to iOS 11 the app will no longer run.
How big of an issue is this? Online sources (Sensor Tower) estimate that at least 8 percent, or about 187,000 apps in the App Store today, do not yet support 64-bit operation.
What's new with iOS 11 with regard to 64-bit support boils down a few key things. If your mobile app is still 32-bit support only:
- It will no longer show up in App Store search results. However, users can get to it for download via a direct link.
- You will have to add 64-bit support in order to send an app update to the App Store.
- Your users will not be able to run your app unless their iOS version is iOS 10.x or below.
- Public-facing App in the Apple App Store. Most likely you've already made the move to support 64-bit. If not, it's imperative you do so before iOS 11 launches.
- Enterprise-facing App in the Apple App Store. If your users are on managed devices running iOS 10.x or below and have a direct download link you're ok for the moment. If your users use their own devices (Bring Your Own Device, or BYOD), you need to add 64-bit support right now.
- Enterprise-facing App in an Enterprise App Store. If your users are on managed devices running iOS 10.x or below you're ok until you decide to upgrade the device OS to iOS 11. However, if you support BYOD, you need to add 64-bit support right now as most users will elect to upgrade to the latest version of iOS as soon as it's available.