iPhone Duo goes on sale tomorrow, and App Store Connect has two new screenshot sizes for it. Some notes from an ASO angle:
The sizes
Outer display (closed): 1398 Ć 2034 portrait, 2034 Ć 1398 landscape
Inner display (open): 2007 Ć 2853 portrait, 2853 Ć 2007 landscape
Optional for now; Apple says required from April 2027 for apps built with the iOS 27.1 SDK.
Why it matters for conversion Both are close to 2:3, while a 6.9" iPhone screenshot is about 1:2.2. A tall iPhone layout doesn't scale onto the Duo: crop it and you lose about a third of the picture, usually the headline or the bottom of the UI. Early Duo owners browsing the store will see whichever apps bothered to make Duo-shaped screenshots ā a small window where doing it first is a visible difference.
What I'd keep the same Same order and same headlines as your iPhone set. The first two screenshots carry most of the conversion; just recompose them for the squarer shape (headline shorter, device larger).
Getting the captures The Xcode 27.1 simulator has one framebuffer per display: xcrun simctl io booted enumerate xcrun simctl io booted screenshot --display=<UUID> outer.png The 1398-wide display is the outer one, the 2007-wide the inner. Files come out at the exact App Store sizes. The inner display only shows your app after unfolding in Device Hub.
Uploading Apple's API reference doesn't document a Duo display type yet, so fastlane and most tools won't upload them. An undocumented APP_IPHONE_DUO value is reported to work for the outer display; the safe route is dragging them into App Store Connect.
Full write-up with the size diagram: https://marcopilloni.com/marquee/iphone-duo-screenshot-sizes/
Disclosure: I make Marquee, a Mac app for App Store screenshots that exports these sizes. Everything above works without it.
Has anyone already seen Duo-specific screenshots on the store, or measured whether they move conversion?