Apple announced iPhone Duo on 9 September 2026, and the developer coverage that appeared immediately was about Swift code — size classes instead of orientation, asymmetric safe areas, stop reading the main screen. All of that is real and Apple documents it.
The App Store half has had less attention, and it is stranger: App Store Connect already lists four iPhone Duo screenshot sizes, does not say whether they are required, does not say what happens if you omit them, and cannot accept them yet.
Four separate facts, each verifiable today. Everything below was checked against Apple's raw markup on 10 September 2026 rather than a summary of it — summarising a long Apple page drops sibling rows, and the rows are the whole story here.
The four sizes
From Apple's screenshot specifications:
| Display | Portrait | Landscape |
|---|---|---|
| Duo outer | 1398 × 2034 | 2034 × 1398 |
| Duo inner | 2007 × 2853 | 2853 × 2007 |
iPhone Duo is the first card in the iPhone section, above the 6.9" card, and the only iPhone entry named for a device rather than a diagonal — every other one is 6.9" Display, 6.5" Display and so on, with a list of the phones it covers. It is also the only iPhone entry with two displays, which no single diagonal names.
Apple's release notes date the addition to 9 September 2026, alongside iPhone 18 Pro Max, iPhone 18 Pro, Apple Watch Ultra 4 and Apple Watch Series 12. iPhone 18 Pro Max joined the existing 6.9" card; the Duo is the only one that needed a card of its own.
The note Apple did not write
Apple's screenshot cards have a second kind of row that matters more than the pixel counts. Most carry a requirement, a scaling note, or both. The 6.3" and 6.1" cards read "If screenshots with the accepted sizes aren't provided, scaled screenshots for 6.5" displays are used." The 6.5" card carries a requirement instead — "Required if app runs on iPhone and screenshots for 6.9" display aren't provided" — and the 13" iPad card reads "Required if app runs on iPad".
Walking every device card in that page's markup, there are eighteen across iPhone, iPad, Mac, Apple TV, Apple Vision Pro and Apple Watch. Sixteen carry a requirement, a scaling note, or both. Two carry neither: the 6.9" iPhone card, and iPhone Duo.
The 6.9" card's silence has an obvious reading: it sits at the top of the iPhone fallback chain, and the 6.5" card points up at it. Apple words the obligation on the row below the one you actually upload, which is why it is still fair to call the 6.9" set the one that satisfies the iPhone requirement, as our August post does.
Nothing anywhere in that table points at the Duo card. No entry falls back to it, and it falls back to nothing. So both of the confident answers you will read over the coming weeks — that Duo screenshots are now required, and that your existing screenshots will be scaled to fill them — are unsourced today. Apple has published dimensions and no policy.
The scaling sentence does genuinely exist for every other row in the iPhone and iPad fallback chains. The moment someone extends it one row upward to cover the Duo, a real rule has become an invented one, which is the hardest kind of error to catch.
You cannot upload them yet
From the App Store Connect release notes, dated 9 September 2026: "Support for uploading assets for iPhone Duo in App Store Connect will be available later this year."
The device ships on 23 October 2026, with pre-orders from 16 October. Apple has published the asset specifications six weeks ahead of the hardware without committing to a date you can act on them. If you are planning a launch-day update, that is the constraint.
Apple's numbers need reading carefully, in two places
The inner display's screenshot size is not the inner display's resolution. Apple's technical specifications give the inner panel as 1878 × 2670 at 430 ppi. App Store Connect asks for 2007 × 2853 — 6.9% larger on each axis, 14.2% more area. Both pages are Apple's and both went live the day after announcement. Searching the specifications page for the words that would explain it — render, downsample, supersample, scale factor, native resolution — returns nothing, and I found no explanation on either page.
The marketing page and the spec sheet describe the shape differently. apple.com/iphone-duo says "The aspect ratio is consistent across the inner and outer display". Divide the numbers on Apple's own spec page and the inner panel is 1 : 1.4217, the outer 1 : 1.4549 — 2.3% apart. "Consistent" is a marketing word rather than a claim of equality, and at 2.3% the sentence is defensible. It is not close enough to lay out one asset against both and expect it to land.
Apple contradicts itself often enough for this to be routine rather than a scandal — the keyword field is 100 bytes on one page and 100 characters on another. Report both halves, and plan against the numbers.
Drawn to scale, the consequence is easier to see than to argue. Every current iPhone screenshot class — 6.9", 6.5", 6.3", 6.1" — sits between 1 : 2.16 and 1 : 2.17. The Duo's two sizes are 1 : 1.42 and 1 : 1.45, and both fall inside the range Apple accepts for the 11" iPad (1 : 1.43 to 1 : 1.52). The only iPhone class in that neighbourhood is the 3.5" one, at 1 : 1.44 and 1 : 1.50, which is the original iPhone through the iPhone 4.
So the Duo's shape is not new to the App Store. It is new to every iPhone anyone has designed for in fifteen years.
The points nobody has
The point dimensions circulating for the Duo — 626 × 890 for the inner display, 466 × 678 for the outer — are arithmetic from an assumed 3× scale factor. Apple has not published one.
That absence is checkable rather than assumed. Apple's Human Interface Guidelines put per-device point specifications on its Layout page, and that page's change log records "Added specifications for iPhone 17, iPhone Air, iPhone 17 Pro" against September 2025, and the iPhone 16 family against September 2024. The 9 September 2026 entry says only that guidance was updated to reflect current best practices. The Duo is named nowhere on it.
The assumption is also stronger for one display than the other, and the number that cuts against it is on Apple's own spec page. The outer panel is 460 ppi, squarely inside the 458–460 band of Apple's 3× iPhones, and 1398 and 2034 both divide by three exactly. The inner panel is 430 ppi. The developer whose arithmetic these figures are labelled them as his own; the label does not always survive being repeated, which is how an assumption becomes a specification in about a week.
What your existing artwork can and cannot supply
If your plan is to regenerate Duo assets from the screenshots already on your listing, it will not work, and the reason is measurable rather than theoretical.
Building the screenshot designer we tested what Apple's image CDN will actually serve for a published listing. Asking mzstatic for the same screenshot at 1290, 2000, 3000 and 4000 pixels wide returned the identical 1242 × 2688 file every time. A store listing serves the developer's original upload and nothing larger. A listing whose screenshots were produced for the 6.5" iPhone cannot supply a genuine 2007 × 2853 image, and upscaling one produces a soft picture.
The aspect ratio makes it worse than a resolution problem. Even a listing sitting at the top of the chain with 1320 × 2868 artwork is at 1 : 2.17, so there is nothing to rescale — the Duo assets have to be composed from source, at a shape no current iPhone uses.
One mechanical rule carries over and is worth restating because it fails silently: Apple accepts .jpeg, .jpg and .png, and states on the same page that images can't include alpha channels or transparencies. A canvas exported as PNG carries an alpha channel whether or not a pixel in it is transparent, and is rejected at upload with nothing on screen to explain why. Export JPEG, which cannot carry alpha by construction, and fill the canvas opaque first — JPEG composites transparency against black.
What Apple does tell you to do
The code guidance is documented and short enough to summarise honestly. From Apple's Tech Talk Prepare your app for iPhone Duo and the new HIG page Designing for iPhone Duo, both published 9 September 2026:
- The SDK you build against is what changes the layout. Your app runs on the Duo without recompiling; the iOS 27 SDK extends it left of the status bar on the inner display, and the iOS 27.1 SDK reaches the screen edge and lays toolbar buttons out vertically.
- Use size classes, not orientation. Apple states that the inner display doesn't honor supported interface orientations, and that it is regular in both dimensions, which leaves room for sidebars.
- Stop reading the main screen. Apple's wording is "Don't reference the main screen on a two-display device", and says it will be deprecated. Use
traitCollection.displayScalerather thanUIScreen.main.scale. - Handle each safe-area edge independently. Insets on opposite sides are often unequal.
ReservedRegionin SwiftUI andUIViewReservedRegionin UIKit are new in iOS 27.1, for custom UI that wants maximum space without colliding with system chrome.
The HIG's summary of all of it is "Avoid fixed widths and display-specific dependencies."
One caveat on tooling: the Tech Talk tells you to download Xcode 27.1 and run the Duo simulator in Device Hub, while Apple's Duo developer page lists Xcode 27.1 beta as coming later this month and the Newsroom describes Device Hub support as upcoming. Two Apple sources out of three say the tooling has not shipped. The Preparing your app for iPhone Duo documentation is listed as pending too.
What none of this tells you
Whether adapting to the Duo does anything for your downloads. Across Apple's HIG page, both specification pages, the Newsroom release, the developer landing page and all six Tech Talks, there is no claim that apps which adapt convert better, rank higher, get featured more or earn more installs. Not a hedged one — none. Apple's two Duo developer surfaces do not mention the App Store at all.
Which apps are worth installing on it. Apple names Netflix, Zoom and Slack as "including" — examples of apps already taking advantage of the device, not a complete set and not a recommendation. That is the whole of what Apple has said. The device is not generally available until 23 October, and we went through what that leaves knowable.
Whether your Duo screenshots will convert. They are a new shape at a size nobody has audience data for. That is measurable only in a Product Page Optimization test inside your own account, and only after uploads open.
What you can do now is the part with a six-week lead time and no dependency on App Store Connect: find your source files and check whether you can compose at 2007 × 2853 at all. If your screenshots exist only as published assets on your own listing, the answer is no — better discovered in September than in October.
The screenshot teardown puts your current screenshots beside the ten apps ranking for a term you care about, at the size a person actually sees them. No model looks at the images, because an automated verdict on creative it cannot see would be confident and worthless.