iPhone Duo App Compatibility Checklist
A practical, interactive checklist to confirm your app is ready for iPhone Duo — size classes, safe areas, Split View, fold handling, and every pose.
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Quick answer
A Duo-ready app avoids hardcoded screen widths and UIScreen.main, supports both Compact and Regular size classes, keeps controls clear of the fold, and has been tested in Split View across every pose. Use the 16-item checklist below to verify your own app, then use the Duo Simulator in Xcode's Device Hub to test each item.
Check off each item as you verify it in your own app. Progress is saved to your browser's local storage — no account needed, and nothing is sent to a server.
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Why it matters
iPhone Duo introduces new width classes, an asymmetric safe area around the fold, and a Split View posture that most existing apps have never been tested against. Apps that assume a single fixed screen size, or that read UIScreen.main directly, are the most likely to break — content can be clipped, controls can land under the fold, or layouts can simply refuse to resize.
How to test each item
Use the Duo Simulator in Xcode's Device Hub to exercise every pose: closed, half-open, fully open, and rotated in each orientation. Resize the app window in Split View and confirm your layout responds to horizontalSizeClass and verticalSizeClass rather than any assumption about device identity.
Frequently asked questions
What is the single most common cause of Duo compatibility bugs?
Reading UIScreen.main or otherwise hardcoding screen width. Both assume a single fixed screen size, which breaks the moment the device folds, unfolds, or is resized in Split View.
Is my progress on this checklist saved anywhere?
Yes, but only in your browser's local storage — there's no account and nothing is sent to a server. Progress will not carry over to a different browser or device.
How do I test every item without physical hardware?
Use the Duo Simulator in Xcode's Device Hub to exercise every pose — closed, half-open, fully open, and rotated in each orientation — and resize the app window to simulate Split View.