With iOS 11 abandoning all support for 32 bit devices and apps, people may be wondering what apps will and will not be supported. The official Apple article linked to above states: "As a reminder, new iOS apps and updates submitted to the App Store must support 64-bit. Support for 32-bit apps is not available in iOS 11 and all 32-bit apps previously installed on a user’s device will not launch." To that end, here's a quick way to determine what apps you have on your device that you will have to leave behind along with iOS 10 itself. This information is available with iOS 10.3 and later.
Go to Settings.
Go to General.
Double Tap the About button.
Scroll down/flick to the Applications button and double tap it. Note that if this just specifies how many apps are on your device, and there is no button available, this means all of your apps are up-to-date and you shouldn't lose support for them when upgrading. How well they will supported, however, remains to be seen when iOS 11 drops this fall. If you do have a button, double tap it.
At the top of this page will be a heading called "compatibility" followed by a list of apps which contain a 64-bit update, and below that, a list of those apps you may have to let go if the developer doesn't update them.
At this time, there are a total of 22 apps on my phone which do not have 64-bit support. If you have apps in this category which you hope to be able to use with iOS 11, I highly encourage you to contact the developer of those apps.