Duo readiness audit
Know exactly what to fix before October 23.
- Every screen run in all 6 poses in the Xcode 27.1 Duo simulator
- Prioritized issue list with screenshots
- Concrete SwiftUI / UIKit fixes for each finding
- Delivered in five business days
iPhone Duo ships October 23, 2026
Is your iOS app ready for iPhone Duo?
Apple's first foldable iPhone has two displays and six poses. Apps built for one portrait screen stretch, clip and collide with the fold. We audit, redesign and test iOS apps for iPhone Duo and foldable devices, and we are building FoldCheck to do it automatically.
- Outer display
- 5.4"
- Inner display
- 7.6"
- Poses to support
- Closed, open and half folded, each in portrait and landscape
What breaks when an iPhone app meets iPhone Duo
Apple says no full refactor is needed, and that is true. But "runs" and "feels native" are different bars. These are the six issues we find in almost every audit.
Size classes ignored
The inner display is regular in both width and height, which is what unlocks split views. Layouts that assume compact width stretch a single column across 7.6 inches.
Safe areas around the fold
iOS 27.1 lays out toolbars vertically and extends content to the screen edge. Custom bars need ReservedRegion or they collide with system UI.
Half-folded pose
A partly folded Duo splits the inner display into two halves. Media, camera and reading views should reflow rather than straddle the crease.
Outer to inner handoff
Opening the device mid-task resizes the window live. State must survive the transition without reloads or lost scroll position.
Side-by-side multitasking
Users run two apps at once on the inner display. Your app can be resized to a compact slice at any moment.
Hardcoded dimensions
Frames built from UIScreen.main.bounds or fixed widths are the number one cause of clipped and overlapping content on Duo.
iPhone Duo key facts for developers
The numbers that decide your layout work. Last updated 2026-09-12.
| Announced | September 9, 2026 |
|---|---|
| Ships | October 23, 2026 |
| Starting price | $1,999 |
| Outer display | 5.4 inches, 1398 x 2034 px, 460 ppi, compact width |
| Inner display | 7.6 inches, 1878 x 2670 px, 430 ppi, regular width and height |
| Poses to support | Six: closed, open and half folded, each in portrait and landscape; plus side-by-side multitasking |
| Legacy apps | Apps built with an SDK older than iOS 27 run letterboxed; iOS 27 extends content past the status bar, iOS 27.1 reaches the screen edge |
| Required tooling | Xcode 27.1, iOS 27.1 SDK, Device Hub simulator |
| New layout API | ReservedRegion (SwiftUI) / UIViewReservedRegion (UIKit), kinds: division (fold), occlusion (camera) |
iPhone Duo consulting
Fixed-price engagements for iOS teams that want their app to feel native on the foldable iPhone without pulling engineers off the roadmap.
Redesign and implementation
We adapt the layouts and ship the pull requests.
- Size-class driven navigation and two-column layouts
- ReservedRegion and safe-area work for custom bars
- Half-fold and multi-window behavior
- Fixed price, quoted from the audit
Ongoing foldable QA
Keep every release Duo-clean.
- Pose and size-class regression pass on each build
- Screenshot diffs across Duo, iPad and Catalyst
- Early access to FoldCheck automation
- Monthly, cancel any time
Early access
FoldCheck: automated iPhone Duo and foldable compatibility testing
The audit, automated. FoldCheck runs your app through every fold pose and size class, finds layout problems, and proposes the code change. Built for iPhone Duo, designed around poses and size classes so it covers iPad multitasking, Mac Catalyst and future foldables too.
- 1
Upload a build
Point FoldCheck at a simulator build or a TestFlight archive.
- 2
Every pose, every screen
It drives the app through all 6 poses (closed, open and half folded, each in portrait and landscape), plus side-by-side multitasking and both size classes.
- 3
Issues, not screenshots
Clipped text, hardcoded widths, overlapping system UI and missing size-class handling are flagged with the offending view.
- 4
Fixes you can merge
Each finding comes with a suggested SwiftUI or UIKit change and a before/after screenshot.
What FoldCheck detects
- Clipped or truncated content
- Hardcoded frame widths and heights
- UIScreen.main.bounds usage
- Missing regular-width layouts
- Custom bars colliding with system UI
- Content straddling the fold crease
- State loss on outer-to-inner handoff
- Broken multi-window resizing
Free for the first apps on the list
We are onboarding a small number of apps before the October launch. Tell us about your app and we will run it through FoldCheck by hand until the tool is self-serve.
Join early accessiPhone 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 questions
Does my existing iOS app work on iPhone Duo without changes?
Usually it launches and runs. Apple lets unmodified apps run on the inner display with limited screen usage that later SDKs extend, but layouts built for a single 6-inch portrait screen often show stretched controls, clipped content, wrong safe areas around the fold, and navigation that ignores the wider size class. It works, but it does not look like a Duo app, and reviews notice.
What is an iPhone Duo readiness audit?
We run your build in the Xcode 27.1 iPhone Duo simulator across all six poses: closed, open and half folded, each in portrait and landscape, plus side-by-side multitasking. Every screen gets screenshots and a prioritized list of layout, safe-area, ReservedRegion, orientation and multi-window issues, with concrete SwiftUI or UIKit fixes. You get the report within five business days.
Which stacks do you support?
SwiftUI and UIKit first. React Native and Flutter apps are supported for the audit and for layout fixes at the native and framework layer.
How long does a full Duo redesign take?
Most apps need one to three weeks. Apps with custom navigation bars, edge-to-edge canvases, or heavy hardcoded widths take longer. The audit gives you a fixed quote before any work starts.
What is FoldCheck?
FoldCheck is an automated compatibility tester for iPhone Duo and other foldable devices. It drives your app through every fold pose and size class, captures screenshots, flags clipped content, hardcoded dimensions, overlapping system UI and missing size-class handling, and proposes code-level fixes. It is in early access; join the list to get in first.
Does this also cover iPad multitasking and other foldables?
Yes. The same adaptive layout work makes your app behave in iPad Split View, Stage Manager and Mac Catalyst windows. FoldCheck is designed around poses and size classes rather than a single device, so it extends to future foldables.
How much does it cost?
Audits and redesigns are fixed price and quoted within 24 hours of your email. FoldCheck early access is free for the first apps on the list.
Ship a real iPhone Duo app before your competitors do
Email us your App Store link. You get a reply with a fixed-price quote within 24 hours.