iPhone Duo black bars in landscape on iOS 27.1

UI Frameworks UIKit
grid OP
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I am implementing support for iPhone Duo, and have seen this in many places:

Apps built with the iOS 27.1 SDK or later are optimized for iPhone Duo. Apps will extend to use the full display, with toolbars and tab bars appearing vertically below the status bar.
(from https://developer.apple.com/iphone-duo/prepare/)

But when I build my application in Xcode 27.1, in both the simulator, and on the Duo hardware, my application is not extending to the full-width of the screen when built for iOS 27.1. There are black bars on both the left and right. When I debug the view hierarchy, I do not see the black bars, which indicates to me this is happening at the OS level, not as a result of my constraints.

Note that there are no black bars in portrait mode, or on the front screen.

In my project settings, only the iPhone Orientation "Portrait" is checked, but I don't want to check Landscape orientations there, because the application does not look good in landscape on a standard iPhone aspect ratio. Are those checkboxes required to remove the black bars? (Checking them does appear to do so, but again, this is quite problematic for the current design of the application.)

Thanks in advance for any insights or help you can provide!

Answered by grid in 914134022

I figured it out. This is the behavior when your Info.plist specifies it requires the full screen. In my case, this was set in the project file with:

INFOPLIST_KEY_UIRequiresFullScreen = YES;

I removed it in the Project -> Info tab.

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grid OP

One additional data point is that this behavior does not happen with a brand new project configured to use UIKit & storyboards, so it is a problem with my project somewhere.
grid OP
Accepted Answer

I figured it out. This is the behavior when your Info.plist specifies it requires the full screen. In my case, this was set in the project file with:

INFOPLIST_KEY_UIRequiresFullScreen = YES;

I removed it in the Project -> Info tab.

DTS Engineer OP
Apple

@grid Thanks so much for your post and providing the answer to your question in less than 1 hour!

This video talks about the UIRequiresFullScreen https://developer.apple.com/videos/play/tech-talks/111461/ You can set it, but you'll should have received a warning in Xcode 27.2?

Thanks
Albert  WWDR