The $1,999 iPhone Duo Has a Black-Bar Problem, and Fixing It Is Harder Than It Looks

Apple announced the iPhone Duo on September 9, its first foldable iPhone, and it went on sale on October 23. The hardware is stunning. But when people unfolded it, they found something they didn't expect: black bars.

Apple mocked black bars. Then it shipped them

On stage at the launch, Apple took a swipe at rival foldables, saying that on them "movies are boxed in by oversized black bars" (as reported by SammyGuru). A few weeks later, the first buyers unfolded their $1,999 iPhone Duo, opened Google Docs or a favourite game, and got... black bars.

This isn't a hardware defect. The 7.6-inch inner screen is gorgeous. The problem is that most of the App Store was built for a phone shape that the Duo simply isn't.

The hardware: a passport that opens into a mini iPad

What you actually see when you open an "old" app

Apple's own developer guide is refreshingly honest. How an app looks on the Duo depends on which SDK the developer built it with:

9to5Mac describes the oldest case bluntly: the app sits "in a safe area around a black background." Apps that get it right show a Made for iPhone Duo badge on the App Store.

Who's ready, and who isn't

On October 22 Apple published a long list of optimised apps, including Netflix, Prime Video, Zoom, Slack, Lyft, Yelp, OpenTable, American Airlines, United and Flighty. Microsoft Word and Outlook are coming "in the coming weeks", and DoorDash later this year.

Reviewers, though, found big names lagging. According to CNN's review (as reported by Gadget Review), Google Maps, Gmail, Uber and Call of Duty Mobile had not been fully adapted before launch. heise found that in Google Docs "the extra screen space was effectively zero", and that games often still show the bar. Wired saw Instagram, Threads and Slack start rolling out better layouts during the review week.

Then comes the long tail: banking apps, government apps, local delivery apps. BGR says many social media, banking, gaming and productivity apps are still not optimised.

Why developers can't just "stretch it"

1. Nearly 20 years of tall-phone habits

Every iPhone since 2007 has been a tall, narrow rectangle. The Duo's inner display is 1878 × 2670 pixels, roughly 1.4:1, which is much closer to an iPad than an iPhone. A single column of cards designed for a narrow screen doesn't scale up. Stretched, it looks like a website from 2009. Real support means a new layout: two columns, sidebars, master-detail views. That's design work, not a checkbox.

2. Screen sizes are hard-coded everywhere

Apple's own guide tells developers to stop reading UIScreen.main and instead react to the real size of the window (view.bounds, GeometryReader, onGeometryChange). Any code that assumed "one phone = one screen width" is now a bug.

// ❌ Assumes one fixed screen. Breaks when the Duo unfolds or enters Split View
let cardWidth = UIScreen.main.bounds.width - 32

// ✅ React to the space your view really has
struct FeedView: View {
    @State private var columns = 1

    var body: some View {
        ScrollView {
            LazyVGrid(columns: Array(repeating: GridItem(.flexible()), count: columns)) {
                // cards…
            }
        }
        .onGeometryChange(for: CGFloat.self) { $0.size.width } action: { width in
            columns = width > 600 ? 2 : 1
        }
    }
}

3. One app, two screens, switching live

The Duo jumps between a 5.4-inch outer screen and a 7.6-inch inner screen while you're using it. Apple says content "reacts as it folds" and switches to the right display. Your app has to survive that mid-scroll, mid-video or mid-typing, without losing state, keyboard focus or a camera session.

4. Navigation moves to the side

On iOS 27.1, system toolbars and tab bars move vertically to the side of the screen. Apps that use Apple's standard components get this for free. Apps with custom tab bars, which is most big brands with their own design systems, have to rebuild them. heise notes Apple isn't automatically moving tab bars for older apps, something that "apparently it's not so easy to implement."

5. Split View on iPhone, for the first time

iPhone Duo lets you open two apps side by side. That means your app no longer controls how wide it is. App studio Improvs points out that UIRequiresFullScreen no longer lets you opt out once you build with the iOS 27 SDK. Your app can be full width now and half width a second later.

6. New APIs, new edge cases

Apple added "arrangement and reserved region APIs", a "hinge API" and "scene accessories". They're powerful, but every one adds states to design and test: closed, open, half-open, landscape and Split View. Developer Christian Selig flagged odd Dynamic Island and Live Activities behaviour on the right side (via BGR).

7. Cross-platform apps wait for their frameworks

Many apps are built with Flutter or React Native. Improvs says Flutter apps get "very little" automatic adaptation because Flutter draws every pixel itself, and React Native apps first need an iOS 27-ready React Native and Expo release. Developers can't ship until their framework does.

8. The timing was brutal

The iOS 27.1 SDK, the only one that unlocks full screen, first appeared in the Xcode 27.1 beta on September 18 (per WorksOnDuo). The Duo went on sale October 23. That's about five weeks to redesign, rebuild, test and pass App Review. Xcode 27.1 does include an iPhone Duo simulator, but the real device costs $1,999, and BGR reported new orders showing delivery dates in late January 2027. Plenty of teams are designing for a phone they haven't held.

9. The money question

For any company, every new screen size means more design, more QA and more maintenance. Right now the Duo is a $1,999 device with a small user base. Big apps will move fast. A bank or ministry app that ships an update every few months may not make it a priority. (That's our analysis, not an official figure.)

Not just apps: the launch's other headaches

• Display cracks: Apple told MacRumors it is aware of "an issue impacting the inner display on a small number of iPhone Duo units", and asked affected owners to contact AppleCare for a replacement.
• Heat: some owners on Reddit say it gets "really hot to the touch" (via BGR).
• Weight: 254g, the heaviest iPhone so far.
• Shipping: per BGR, new orders were slipping to late January 2027.

So... should you buy one?

The official price is $1,999 for 256GB, up to $3,199 for 2TB. These are US prices, and local prices in Kurdistan may differ.

If your daily apps are Apple's own plus Netflix, Zoom and Slack, you're in good shape. If your life runs on Google apps, banking apps and games, wait a few months and look for the Made for iPhone Duo badge on the App Store.

For developers: a 5-minute triage

• Build with Xcode 27.1 and the iOS 27.1 SDK, and run the iPhone Duo simulator.
• Search your code for UIScreen.main, fixed widths and device-model checks.
• Swap custom tab bars for system ones, or teach them to move to the side.
• Test every pose: closed, open, half-open, landscape and Split View.
• Check Live Activities and the Dynamic Island on the side of the screen.