iPhone Duo & Foldables in iOS 27: The Complete Developer Guide
iPhone Duo is Apple's first folding iPhone — an outer display for one-handed use and a wider inner display for multitasking, joined by a hinge that apps can query and react to directly. It ships with a reimagined iOS built around resizability: two size classes instead of interface orientation, reserved regions instead of hardcoded coordinates, and layout containers that adapt automatically as the device opens and closes.
Build against the iOS 27 / 27.1 SDK and simulate every pose with the DeviceHub simulator in Xcode — no hardware required to get started. Here's every iPhone Duo capability tracked in SwiftChronicle, sourced from Apple's iPhone Duo Tech Talks.
New in iOS 27
The foundational adaptation layer for iPhone Duo: build against the iOS 27 / 27.1 SDK, simulate poses with DeviceHub in Xcode, and use size classes (not interface orientation) to lay out across the outer and inner displays.
Apple’s design system for iPhone Duo’s reimagined iOS: controls move to the outer edge, content displaces away from the hinge, and interfaces adapt across held, used, and folded poses.
APIs for observing continuous hinge angle and open/closed state (onHingeChange / UIHingeInteraction), plus scene accessories that present supplementary content on iPhone Duo’s second display simultaneously with the main UI.
New toolbar, tab bar, and navigation bar axis behavior for iPhone Duo’s wider aspect ratio, where top/bottom controls move to a shared vertical region along the side of the display.
A new layout container (ArrangementView in SwiftUI, UIArrangementViewController in UIKit) for split and overlay presentations that automatically query reserved regions — the hinge and camera housings — on iPhone Duo.
iPhone Duo’s two front cameras — an outer ultrawide and the first under-display inner ultrawide on iPhone — exposed individually via AVFoundation, plus a Virtual Front Camera that switches between them automatically as the device opens and closes.
Browse Foldables capabilities interactively
Filter by framework, see the full code demos, and track implementation gotchas for every iPhone Duo API.
Foldables capabilities in SwiftChronicle