What an unadopted app actually does on Duo, and what is required before launch

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Created 11h

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This post is from the Activity iPhone Duo UIKit Q&A.

Our app is a standard iPhone app (iOS 15 and later). Guidance so far is that an app that ignores ArrangementView, reserved regions, and the hinge keeps its existing iPhone size. On a folded Duo, does that mean letterboxed on one half, scaled on the outer display, or a normal compact layout on the cover screen? Is any of the six new APIs required for App Store review, or can we ship with size-class adaptation only and adopt arrangements after the October 23 launch?

Answer 1

DTS Engineer OP

Apple

11h

While your app is built with Xcode 26 or older, you'll be in a compatibility mode. It works like this:

With iPhone Duo closed, your app on the outer display uses the region of this display outside of the vertical bar.
With the device fully open and only a single app open, the app is centered on the display in this same familiar size and aspect ratio, and if the device is only partially open, the app shifts to one side of the display, while at the same size.
If iPhone Duo is fully open and your app is one of two running in split screen multi-tasking, the same size and aspect ration remain true, regardless if your app is on either side of the display.

Modernizing your app to take full advantage of the iPhone Duo display starts with tasks like size class adaptation, and ensuring your app's layout is flexible. Using the additional APIs that are helpful on iPhone Duo come after you've done that initial work — not every app needs to use Arrangement Views or the reserved regions API, it really depends on an case by case basis of what will make your app great after that initial work.