Apple has required all new iOS apps and app updates submitted to the iOS App Store to support 64-bit since June of 2015. Since then, Apple has begun phasing out support for 32-bit apps, and plans to stop supporting them all together with iOS 11.
While Apple has enforced 64-bit support for several years, there are still a number of older iOS apps that have not been updated since 2015 but remain in use. When attempting to open a 32-bit app on iOS 11, it will not run and users will see a popup that says "The developer of this app needs to update it to work with iOS 11."
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. If you haven't updated your app on the App Store to support 64-bit, we recommend submitting an update so your users can continue to run your apps on iOS 11, which will be in the hands of hundreds of millions of customers this fall.
At WWDC, Apple announced plans to start phasing out 32-bit Mac App Store apps as well. Starting in January of 2018, Apple will require all new Mac apps submitted to the Mac App Store to support 64-bit, and all existing apps must implement support by June of 2018. According to Apple, macOS High Sierra will be the last version of macOS that will support 32-bit apps "without compromise."
At WWDC 2017, we announced new apps submitted to the Mac App Store must support 64-bit starting January 2018, and Mac app updates and existing apps must support 64-bit starting June 2018. If you distribute your apps outside the Mac App Store, we highly recommend distributing 64-bit binaries to make sure your users can continue to run your apps on future versions of macOS. macOS High Sierra will be the last macOS release to support 32-bit apps without compromise.
When phasing out 32-bit apps on iOS devices, Apple gave both end users and developers ample notice and several warnings, and the company plans to follow the same path as it phases out 32-bit Mac apps.
Along with reminding developers about its app requirements, Apple today also announced the availability of transcripts for all of its WWDC 2017 videos, making it easier for users to find and share specific information that was covered at the event. Transcripts can be searched by keyword, with those keywords linked to the specific times when they were mentioned.
Apple's session videos cover a wide range of topics, including Core ML, ARKit, Metal 2, Drag and Drop, Swift, Touch Bar, CareKit, tvOS, and much, much more.