Apple iPhone Duo: Developers can now submit optimized apps

With just over two and a half weeks to go before the iPhone Duo launches, Apple has opened the App Store to apps tailored to its foldable iPhone. In a notice to developers, Apple says optimized apps and games can now be submitted through App Store Connect. The iPhone Duo goes on sale October 23, starting at $1,999 in the US. Preorders open October 12.

What do developers need to do? In the simplest case, recompile their apps. Rebuilding an existing app with Xcode 27.1 adds development support for the iPhone Duo. Xcode's Device Hub shows how the app behaves in every device posture and orientation, an important consideration for a foldable that is frequently closed, opened and rotated during everyday use.

Unmodified apps will have black borders

Existing apps will run on the iPhone Duo without an update, but they will not use the entire display. As MacRumors reports, only apps built with the SDK for iOS 27.1 or later will fill the inner display. All others will appear with black borders, a noticeable drawback on a device bought primarily for its large folding screen.

To encourage developers to address this, Apple has set a deadline: starting in April 2027, all submitted apps and games must include screenshots for the iPhone Duo. Apple has already updated its screenshot and app preview requirements, while a new preview tool in App Store Connect shows how an app's product page will look on the Duo. Workshops around the world will also help developers optimize their apps for the new format.

A separate device category in the App Store

The screenshot requirement sends the clearest message. It does not force developers to adapt their apps, but it makes clear that Apple will treat the Duo as a distinct device category in the App Store over the long term, rather than a niche product supported as an afterthought. For buyers, however, that still means not every app will take advantage of the large display at launch on October 23. How quickly the major apps catch up is up to their developers, and Apple has now made it possible for them to get started.