Michael JohnsonWith a foldable iPhone, one screen scenario quickly becomes several: users open an app on the outer display, unfold the device, rotate it, and open a second app alongside it. Apple has added support for iPhone Duo in Xcode 27.1 and recommends testing app behavior in Device Hub in different device positions and orientations. So the team’s first task is to check how the interface adapts when the available space changes.
iPhone Duo will go on sale on October 23, 2026, with pre-orders starting on October 16. Apple’s developer guidance says that apps can already be submitted through App Store Connect. Starting in April 2027, submissions of apps and games will need to include screenshots for iPhone Duo. This divides preparation into two stages: functional testing before sales begin, and preparation of the product page’s required materials by next spring.
Rebuild the app first
Apple recommends rebuilding your existing app with Xcode 27.1, which adds support for iPhone Duo. After building, open the app in Device Hub and test it in the available device positions and orientations.
Make a list of screens with dense layouts: forms, long lists, tables, media players, control panels, and screens with a keyboard. For each one, check that important elements remain visible, key actions are accessible, and user-entered data is preserved when the device changes position. These are practical checks of adaptive behavior; specific requirements depend on the app’s features.
Test transitions between displays
Apple gives the iPhone Duo’s outer display a diagonal measurement of 5.4 inches and the inner display a measurement of 7.6 inches. In its announcement, the company describes content adapting when the device is folded, its orientation changes, or users switch to the other display. New and updated APIs are available to developers in the latest SDKs. Test a complete workflow: start an action on the outer screen, unfold the device, rotate it, and continue.
Also check the app’s state after switching displays: drafts, filters, list position, and playback progress, if they matter to its features. Test the reverse route too, from the inner screen to the outer one. If your app uses custom navigation or fixed-width panels, test them at every display-area size.
Test Split View and app switching
Apple says iPhone Duo supports Split View, allowing users to open two apps side by side. Users can also switch quickly between apps and save app pairs. Test core features in a narrower screen area: text readability, navigation access, and the placement of important buttons.
Apple also gives two Safari windows as an example of using multiple windows in one app. If your app supports multiple windows, test how two instances work together, what data they show, and how users return to the window they need. If this mode isn’t implemented, test the app alongside another one and after switching back to it.
Prepare the app’s product page
Apple has published updated specifications for screenshots and previews for new devices, including iPhone Duo. App Store Connect now has a tool for seeing how screenshots, page titles, and other materials will look on the device’s product page. Follow Apple’s App Store asset guidance and check the layout for the supported orientations.
The workflow is: rebuild the app in Xcode 27.1, run through scenarios in Device Hub, test Split View and app switching, then prepare the product page materials and review them in App Store Connect. The device will go on sale on October 23, 2026; screenshots for iPhone Duo will become mandatory for new App Store submissions in April 2027.