Apple has opened App Store submissions for apps optimised for iPhone Duo, its first foldable, ahead of a launch on Friday 23 October. Pre-orders are reported to start on 16 October.
The detail that matters to anyone who owns an iPhone app: only apps built with the iOS 27.1 SDK or later can resize to fill the whole inner display. Existing apps will still run on the Duo automatically, but without that work they appear with black borders around them. Apple has published guidance, and the practical step is building with Xcode 27.1.
How to read this
Nothing breaks. Your app will launch. But on launch day, the first people to buy a new £1,000-plus device will be your most engaged, most vocal users, and they will be looking at an app that looks unfinished next to competitors that have adapted.
This is the same pattern as iPad, and more recently the larger-screen rules on Android: a new screen shape arrives, and apps that were never designed to flex are the ones that look dated. Apps built with flexible layouts need a light touch. Apps with fixed layouts, hard-coded sizes or a long-neglected codebase need real work.
Questions to ask your app team this week
- Has the app been built and tested against the iOS 27.1 SDK?
- Does it use flexible layouts, or fixed screen assumptions?
- Which screens matter most on a larger inner display: forms, dashboards, media, checkout?
- Can an update be submitted and approved before 23 October, and if not, when?
So what
A foldable will be a small share of your users at first, so this is not an emergency. It is a good, cheap test of whether your app is built to last. If the answer is “we would need to rebuild half of it”, that is worth knowing now. If you need a view on how adaptable your iOS app is, our iOS and Android development team can review it, or you can start a project and we will tell you plainly what it would take.