Apps and games for iPhone Duo: what changes, what to expect from an app and how to spot one

What changes on iPhone Duo?

Two displays. A 5.4-inch outer one, used closed like a regular iPhone, and a 7.6-inch inner one that opens like a notebook; Apple describes it as fifty percent larger than the iPhone 18 Pro Max display. Both are Super Retina XDR with ProMotion up to 120 Hz, Always On and 3,000 nits peak brightness; the inner one has a nano-texture finish that cuts glare and hides the crease.

Three postures. Closed, book (both halves at an angle, standing on the table like a laptop or an open book) and fully open. iOS 27.1 gives apps a hinge API that tells them which posture the phone is in and exactly where the fold runs, so they can put something right on it or stay clear of it.

Split View. For the first time on an iPhone, two apps at once on the inner display, one on each half: Photos on one side and Mail on the other, dragging pictures across. Also two windows of the same app, and saved app pairs that open together.

The Dynamic Island moves. On the inner display the island sits vertically on one side. It is a detail that separates careful apps from the rest: a stretched app puts buttons underneath it.

The outer display for the camera. Open, the outer display works as a viewfinder for the person in front (Duo Preview), shows animations so children look at the lens (Kid Cue), enables selfies with the 48 MP rear cameras and lets someone nearby join a FaceTime call. The FaceTime camera hides under the inner display.

The rest. A20 Pro chip, grade 5 titanium frame and hinge cover, a hinge of more than a hundred parts, IP68, a fingerprint reader in the side button and a dual battery: up to 31 hours of video on the inner display and 44 on the outer. Pre-orders from 16 October 2026; on sale 23 October, from $1,999.

What can an app do on iPhone Duo that it cannot do on a regular iPhone?

Stretching is not enough. A regular phone app looks fine on the inner display, but it is still a single-screen app. The difference is using the fold, and there are exactly four ways to do it.

The hinge as part of the content. If the centre of the screen is a meaningful place (the bar of a backgammon board, the spine of a book, the net of a board, the river in xiangqi), the app can put it on the physical fold instead of avoiding it. It is the most striking way, and the rarest.

Book posture as privacy. With the phone standing up, each half faces a different person. It is the natural posture for two players, for showing something to the person across from you without them seeing your side, or for video on one half and controls on the other.

Closing as a gesture. Closing the phone is an event the app can listen to: pause, hide information, pass the turn to the other player. No flat phone has that gesture.

Two displays, one state. What you were doing must not be lost when you open or close the phone, move from the outer display to the inner one or enter Split View. It sounds obvious and it is where many apps fail.

What to expect from each kind of app

Games for two people. The hinge as the board, book posture to hide hands and cards, and closing to pass the turn with hidden information. It is the genre where the foldable adds the most, because two people with a hinge between them is a table.

Reading and notes. Two pages open like a book, with the fold at the spine; in book posture, the text above and the notes below. If the app shows one stretched column across 7.6 inches, it is not adapted.

Photos and video. A viewfinder on the outer display for whoever is posing, selfies with the rear cameras and, in book posture, the video on the top half and the controls on the bottom one, no tripod needed.

Productivity and messaging. Split View with saved pairs (mail and calendar, chat and document), drag and drop between the halves, and nothing important hidden under the Dynamic Island. At the launch event Apple showed adapted versions of Netflix, Zoom, Slack and Detail.

Video and calls. Full-screen landscape on the inner display; in book posture the phone stands on its own; and the outer display can bring someone else into the call.

How to spot an app built for the Duo on the App Store

Apps compiled with the Duo SDK carry a badge on their product page saying they are optimised for iPhone Duo, and can show screenshots of the inner and outer displays. If a page only has regular iPhone screenshots, the app most likely does nothing with the fold.

Searching for “iPhone Duo” on the App Store is the quickest way to find the first apps built for it. The description matters too: if it does not mention the foldable, the hinge or book posture, it is usually not adapted.

Board games for two on iPhone Duo: the Tapete example

Tapete is a case of fourteen board games for two people sharing one phone, designed for the Duo from day one: no AI opponent and no online play, just two people and the phone between them. Sea battle, four in a row and air hockey are free; the other eleven unlock with a single purchase, shared with the family. No accounts, no ads, no data collection. And on any other iPhone or iPad it plays the same, with a “pass the phone” curtain.

How each game uses the fold

• Sea battle: place your fleet full screen, close the phone and hand it over: closing passes the turn. Free.
• Four in a row: the frame stands on the hinge and each half shows one face. Free.
• Backgammon: a shared board across the width; the bar is the hinge.
• Chess with clock: one board per half, each from its own side, and a 5 minutes plus 3 seconds clock.
• Draughts: Spanish draughts, one board per half.
• Brisca: in book posture each player sees only their own hand; flat, the cards go face down.
• Xiangqi: the board turns sideways and the river is the hinge.
• Go: a 9×9 or 13×13 board centred on the fold.
• Dominoes: private tiles in book posture; double six to 100 points.
• Tute: private hands in book posture, declarations and last trick.

Checklist: 7 signs an app is built for iPhone Duo

1. It carries the “optimised for iPhone Duo” badge on its App Store page.
2. It shows screenshots of the inner and outer displays, not just regular iPhone ones.
3. It works in Split View at half the screen without breaking or hiding buttons.
4. It puts nothing important under the vertical Dynamic Island.
5. It does something different in book posture (two halves with different roles, or for two people).
6. It reacts when the phone closes: pause, hide or pass the turn.
7. It keeps what you were doing when you fold, unfold or switch displays.

Glossary

Inner display

The 7.6-inch display revealed when you open iPhone Duo; the one that can split into two halves.

Outer display

The 5.4-inch display used with the phone closed, like a regular iPhone.

Fold

The centre line of the inner display, where the phone bends. iOS exposes it to apps as a reserved region.

Book posture

The phone open at an angle, standing on the table; each half faces one side.

Hinge API

The iOS 27.1 interface that tells an app whether the phone is closed, in book posture or open, and where the fold runs.

Split View

Two apps, or two windows of the same app, side by side on the inner display.

Vertical Dynamic Island

On the inner display the island sits on one side, vertically, and reduces the usable area of that edge.

Optimisation badge

The mark on an App Store page showing the app was compiled for iPhone Duo.

Close and pass

A game mechanic where closing the phone hides your information and passes the turn to the other player.