iPhone Duo developer guides
Free, practical references written from Apple's developer materials. Also available as Markdown for AI assistants.
How to prepare your iOS app for iPhone Duo: a 12-step checklist
A practical checklist for making an existing iOS app work well on iPhone Duo before its October 23, 2026 launch: size classes, ReservedRegion, safe areas, poses, multitasking and testing in the Xcode 27.1 simulator.
7 min read
iPhone Duo specs for developers: displays, size classes, poses and tools
The iPhone Duo facts that matter when adapting an app: outer and inner display sizes and resolutions, size classes per pose, the fold and camera reserved regions, SDK versions and simulator tooling.
4 min read
SwiftUI and UIKit layouts for iPhone Duo: size classes, split views and reserved regions
Code-level guidance for adapting SwiftUI and UIKit layouts to iPhone Duo: reading size classes, using NavigationSplitView, dropping UIScreen.main.bounds, and respecting the fold and camera reserved regions.
8 min read
iPhone Duo testing checklist: the pose matrix every screen must pass
A QA matrix for iPhone Duo and foldable devices: which poses and size classes to test, what visual defects to look for, how to use the Xcode 27.1 simulator, and how to automate the run.
5 min read
iPhone Duo app letterboxed or not full screen: why it happens and how to fix it
Why an existing iOS app shows black bars or does not fill the inner display on iPhone Duo, and the exact steps to fix it: rebuild with Xcode 27.1, adopt size classes, remove fixed dimensions and handle reserved regions.
5 min read
How much does it cost to update an app for iPhone Duo?
Realistic effort and cost ranges for making an iOS app work well on iPhone Duo, by app type, with the factors that move the estimate up or down and what a fixed-price audit covers.
6 min read
iPhone Duo support for React Native and Flutter apps
What cross-platform iOS apps need for iPhone Duo: window dimensions that update on fold and unfold, safe areas around the fold, size-class equivalents, and where native code is still required.
7 min read
iPhone Duo design guidelines for product teams
Design rules for iPhone Duo apps aimed at designers and product managers: continuity between displays, two-column layouts on the inner display, the half-fold pose, the fold and camera regions, and what to hand engineering.
6 min read