Xcode 27 backward compatibility mode (black bars)

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

When building with Xcode 27, is there any way (e.g. key in info.plist file) to get the backward compatible UI mode (black bars around - like when you build with Xcode 26)?

Answered by DTS Engineer in 906453022

When your app is built with Xcode 26, it will be in a compatibility mode that keeps a familiar size and aspect ratio that's similar to a device like iPhone 17. When you move forward to building with Xcode 27, your app expands to fill most of the screen on iPhone Duo, except for the vertical bar. And then when you build with Xcode 27.1, your app fills the complete screen, and begins to use the vertical bar. All of these changes are based on what SDK version you build your app with — there aren't any Info.plist keys for these behaviors.

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DTS Engineer OP

Apple

13h

Accepted Answer

When your app is built with Xcode 26, it will be in a compatibility mode that keeps a familiar size and aspect ratio that's similar to a device like iPhone 17. When you move forward to building with Xcode 27, your app expands to fill most of the screen on iPhone Duo, except for the vertical bar. And then when you build with Xcode 27.1, your app fills the complete screen, and begins to use the vertical bar. All of these changes are based on what SDK version you build your app with — there aren't any Info.plist keys for these behaviors.