iphone-duo
Adapting apps to iPhone Duo
An implementation guide based on six Apple Tech Talks, the Human Interface Guidelines, Apple Developer Documentation, and two iPhone Duo Group Labs (2026-09-16 and 2026-09-17) as primary sources.
App Store Connect accepts optimized apps starting on 2026-10-05. iPhone Duo screenshots are required for submissions from 2027-04 onward.
Start here
iPhone Duo launches on 2026-10-23 with iOS 27.1. The SDK with iPhone Duo support and Device Hub are included in Xcode 27.1 (beta released on 2026-09-18, Release Candidate on 2026-10-05).
iPhone Duo has two displays, inner and outer, and opens and closes around a central hinge. Your app remains an iPhone app; opening and closing cause a resize. There is no dedicated user interface idiom: it returns phone. The only new aspect is that the inner display has regular size classes on both the horizontal and vertical axes, a first for iPhone.
An app running full screen on the inner display moves to the outer display when the device closes and keeps running. It does not enter the background. Split View is the exception: with two apps side by side, the most recently used app moves to the outer display and the other enters the background. If you reopen immediately, both return; after a delay, the app that was on the outer display fills the inner display.
The foundation is a layout that handles resizing. Existing support for resizing on iPad or through iPhone Mirroring carries over directly.