How to tell if an app is made for iPhone Duo

1. Look for the badge

Developers who submit screenshots for both iPhone Duo screens get an "optimized for iPhone Duo" badge on their App Store page. No badge does not always mean a bad app, but it is the quickest signal.

2. Open the phone in the middle of something

Apple's guidance is that folding or unfolding is a resize, never a relaunch. Type half a message, scroll down a page, then open the phone. A well-built app keeps your text and your place.

An app that jumps back to the start has treated the two screens as two separate layouts.

3. Check where the buttons are

On iPhone Duo the system puts toolbars and tab bars in a vertical column on the right edge. Apps built with the iOS 27.1 SDK get it; apps built with an older SDK sit letterboxed, with empty space around them.

Also notice whether anything you have to tap sits on the fold in the middle of the inner screen. Apple's guidance is to keep it away from the curve.

4. Try every pose

Apple tells developers not to tie a feature to one pose. Half-open like a laptop, propped like a tent or flat, the same controls should be there.

Apple names Netflix, Zoom and Slack as apps that already use the folding design.

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