For developers

Getting your app ready for iPhone Duo: a developer checklist

Rebuild with Xcode 27.1, test every posture, ship before October 23 and plan for the April 2027 screenshot rule. A practical checklist with links to Apple's announcements.

By Festim Peposhi · Updated October 12, 2026

Short answer

Recompile your app with Xcode 27.1 so it can use iPhone Duo's whole inner display, test it folded, unfolded and half-open, and submit it in App Store Connect now: iPhone Duo goes on sale on October 23, 2026. iOS 27 builds fill only most of the display, and older builds run letterboxed. From April 2027, every submission needs iPhone Duo screenshots.

Key dates

October 5, 2026: App Store Connect accepts iPhone Duo-optimized apps and games.
October 16: pre-orders open.
October 23: iPhone Duo is in stores. Your users start seeing your app on it.
April 2027: new submissions must include iPhone Duo screenshots.

The checklist

1. Recompile with Xcode 27.1

Apple's announcement puts it simply:

Recompile existing apps with Xcode 27.1, which adds development support for iPhone Duo.

Apple describes three tiers. Builds made with the iOS 27.1 SDK or later use the full display, with toolbars and tab bars appearing vertically below the status bar, so check your content adapts to that. iOS 27 SDK builds fill most of the inner display but avoid the status bar on the right edge. Older builds appear in the middle of the display with empty space around them. If your layout is already adaptive, a rebuild may be most of the work.

2. Find what breaks at the new size

Hard-coded screen widths or heights, and checks that assume a specific iPhone model.
Layouts locked to portrait, or full-width lists and images that look stretched on a wide screen.
Custom keyboards, sheets and popovers sized for a narrow phone.
Games and video with a fixed aspect ratio: decide whether to letterbox inside your own UI or reflow.

3. Test every posture

Use the Xcode 27.1 Simulator and Device Hub to check the outer screen, the inner display in portrait and landscape, and the half-folded tabletop position. Then test the transitions, not just the end states: fold and unfold while typing, while a video plays and in the middle of a checkout. The app should keep its place without restarting or losing input.

4. Use the extra space

Filling the screen is the minimum. Apps that feel designed for Duo show more at once: a list beside the selected item, a sidebar, a second column, or controls on the lower half when the phone is propped open. That's the difference between “Fills the screen” and “Built for Duo” in our directory.

5. Submit early

Submissions go through normal App Review, and Apple hasn't announced a faster track, so leave time before October 23 for a rejection and resubmission.

6. Say so in your release notes

Write “iPhone Duo” in your release notes when you ship support. Owners look for it, and our update tracker picks it up automatically and highlights your update, with a link to your App Store page.

7. Plan your screenshots

Apple's other deadline is about your product page:

Starting April 2027, any apps or games submitted will need to include screenshots for iPhone Duo.

Showing a real Duo layout in those screenshots is also the clearest way to tell people your app is ready.

8. Show your status

Every app in our directory has a live badge that shows its current iPhone Duo status and updates by itself as owners report:

Find your app on the developers page and copy the Markdown or HTML into your README, website or press kit.

See what owners report about your app

Search for your app in the directory, or add it if it's missing. Its page shows how owners say it runs, which positions cause trouble, and how many people are waiting for Duo support. Shipped an update? Email the release notes link to festim@oda.al and we'll check it and add it to the tracker.