Apple’s own iPhone Duo simulator, online and streamed from our Macs. Test your app on it in a browser tab: fold it to a preset or an exact hinge angle, rotate it in any posture, and let your coding agent do the same.
The iPhone Duo simulator, folding in a browser tab.
Apple announced the iPhone Duo on September 9:
a 5.4-inch cover screen outside and a 7.6-inch folding screen inside, shipping on iOS 27.1.
To build for it locally you need Xcode 27.1, which needs macOS 26.6 or later
and an Apple silicon Mac. VibeView cloud builds can make that build instead.
If you searched for an iPhone Fold simulator, you’re in the right place: Apple named its foldable iPhone the iPhone Duo, and this is its simulator.
VibeView runs that simulator for you. Pick iPhone Duo (iOS 27.1) in the device picker, where it carries a
Foldable badge, and your app starts on the cover screen in a browser tab. There is no Xcode download, no
runtime to update and no Mac on your desk.
Test your app on iPhone Duo, not a viewport mock-up
Search for an iPhone Duo simulator online, or an iPhone Duo emulator, and most results are web pages that resize a website to the Duo’s two screen sizes. That is
useful for a responsive site. It cannot install a native app, run iOS or fold anything.
Here your app runs on Apple’s iPhone Duo simulator itself: iOS 27.1, a hinge angle the system reacts to, and
two screens that hand over to each other as the device folds. If your app reads the hinge, switches layouts when the device
opens or rotates on the inner screen, this is where those code paths actually run.
Fold to a preset or an angle
Closed, Partial and Open are one click each. Turn on Set by angle to drag to any whole angle from 0 to 180 degrees.
Rotate in any posture
Each press turns the device a quarter clockwise, closed, half-open or flat. Apps that support the new orientation turn their layout.
Both screens, live
Where your browser supports it, the Duo is drawn as a 3D model that folds with the hinge, with each screen showing what it is displaying.
An agent can fold it too
The VibeView CLI and MCP server give your coding agent the same controls: start on the Duo, set a posture or an angle, rotate.
Posture · Hinge angle
Fold it the way a person would.
Starts closed, on the cover screenThe device’s normal at-rest state. Add ?posture=open or ?posture=partial to the sandbox URL to start unfolded instead.
Three presets and a sliderPartial opens it partway and hands over to the inner screen; Open lays it flat, inner screen in landscape. The hinge moves smoothly, so the screens change over within about a second, as they do on the device.
The device decides which screen is litJust like the hardware, it can keep the inner screen on until the hinge is nearly shut, so the same angle can land differently depending on the direction you came from. Taps always go to the screen in use.
Is your app optimized for iPhone Duo? Check without buying one
Apple’s preparation guide says apps
built with the iOS 27.1 SDK or later are optimized for iPhone Duo and fill the whole inner display. It adds that
there your app should look like a natural extension of its iPad layout and keep up with every size change a fold
brings. You can declare support for all device poses in App Store Connect. A VibeView session shows you all of
this in a browser tab, on Apple’s own Duo simulator.
It now matters on the App Store too. Apple announced on October 5
that an app gets a badge on its product page saying it is optimized for iPhone Duo once you submit iPhone Duo
screenshots. Apple’s
screenshot specifications
add that from April 2027, apps built with the iOS 27.1 SDK or later must include Duo screenshots.
What an app that isn’t optimized looks like
Which of these you see on the inner screen comes down to the iOS SDK your build used:
Older than the iOS 27 SDK: your app keeps its iPhone width, centered, with black bars to the left and
right. Apple’s preparation guide
says these apps run on the Duo but “won’t adapt to all layouts.”
The iOS 27.0 SDK: the app stretches across most of the screen, so a two-pane layout can appear. It
still doesn’t know where the fold is, and the status bar strip along one edge stays black.
The iOS 27.1 SDK or newer: the app fills the whole inner screen and can put content on either side of
the fold.
Apple’s guide describes the same behavior on the phone itself, so this is what your users will see.
Check your app’s layout on the Duo
Upload your simulator build, or make one with a cloud build. Cloud builds use Xcode
26.5 unless you add "xcode": "27.1" to the iOS build block, which the full inner screen needs.
A build with the iOS 27 SDK must use the scene-based life cycle, or iOS won’t open it:
fix the UIScene launch error first.
Pick iPhone Duo (iOS 27.1) and open your app. It starts closed, on the cover screen.
Choose Open to unfold it. If VibeView can tell your build used an earlier SDK, a short note says so
while the inner screen is in use.
Choose Partial, or turn on Set by angle in the Device tab and drag the hinge. Watch
the layout as the device hands over from one screen to the other, then rotate it in each posture.
Send a share link set to the Duo so a reviewer can look too.
Look for a layout stuck at phone width, content cut by the fold, and screens that don’t redraw when the device folds or
turns.
Check your own build on the Duo. The Free plan includes 30 streaming minutes a month and
needs no card. Start free.
Rotate it in any posture
The Rotate button beside the device, and the Orientation control in the Device tab, turn the Duo a quarter turn clockwise each
press: portrait, landscape, upside down, landscape the other way, then back. It works closed, half-open and open. The 3D model
turns with it, and the screen shows what your app does with the new orientation: an app that supports it turns its layout to
stay upright, while the Home screen and portrait-only apps turn with the device.
Both screens, live
In a browser that can draw it, the session is a 3D model of the Duo that folds along with the posture you set, and you tap and
drag directly on whichever screen is open. Both screens stay live on the model: your app on the screen in use, the device’s own
fold animation on the other while the hinge moves, and black once it settles off. Where the 3D model is not available, a flat
view shows the screen the device is using, live and tappable at any angle.
One thing worth knowing about sizes: the simulator’s inner screen reports 2007 × 2853 pixels, larger than the 1878 × 2670
Apple lists for the hardware. The cover matches at 1398 × 2034.
Test layout in points and size classes, not by pixel-matching screenshots against the device.
Share a folding demo
A share link is an ordinary URL: pick the iPhone Duo as its device and the person you send it
to opens your app on the Duo in their browser, with no install and no account. To put it in your own page, an
embed key can include the Duo as well, and ?posture=open on the iframe starts it
already unfolded. Embedding needs Team or above.
Drive it from an agent
Apple ships no command to set the hinge angle; simctl has nothing for it, and Device Hub’s slider is a mouse
control. VibeView’s CLI (0.23.0 and later) and its MCP server expose the fold as commands your
coding agent or CI job can call:
vibeview list-devices --models # the Duo is marked "foldable"
vibeview dev --detach --json --model "iPhone Duo"
vibeview set-posture partial --session <id>
vibeview set-posture --angle 75 --session <id>
vibeview rotate --degrees 270 --session <id>
Each response says where the device ended up: the posture it settled in, the hinge angle and the size of the screen now
showing (with an angle, also which screen is lit), or the new orientation. Folding changes the screen, so earlier element references are stale and the response carries the new one.
Over MCP the same controls are list_device_models, dev_start with a model,
set_posture and rotate. Agent Control lists every command, and
this guide walks through a fold test from a script.
In VibeView’s own AI tests, the agent can fold the Duo to Closed, Partial or Open as a test step. AI testing is in beta.
What this does not do
Apple’s simulator, Apple’s updates. The Duo runs Apple’s iOS 27.1 simulator, so its behavior can change as
Apple ships updates.
A simulator, not an iPhone Duo. There is no physical Duo here. Camera, real hinge feel, sensors, performance,
battery and thermal behavior are not simulated, and the inner screen’s pixel size differs from the hardware’s. Keep a pass on
the device before release; simulator vs real device testing covers where the
line falls.
One screen in use at a time. Part-way through a fold the device can keep the cover in use while the inner
screen faces you. Taps on the screen that is not in use are ignored until the device switches, which it normally does as the
fold settles.
It runs simulator builds. An .ipa is a device build and is rejected at upload. React Native and
Expo projects can skip the local toolchain: cloud builds compile the simulator build
from Windows or Linux and drop it straight into your app, ready to open on the Duo. For other projects,
preparing your build has the command.
The Duo is priced like any other device. Pricing is per organization rather than per seat, and streaming minutes are metered on
every plan. The free tier is 2 concurrent sessions, 30 streaming minutes a month, $1 of usage credit
refilling monthly, for one person and no card, with each free session ending after 5 minutes.
Frequently asked questions
Is this the real iPhone Duo simulator or a mock-up?
It is Apple’s own iPhone Duo simulator on iOS 27.1, running on our Macs and streamed to your browser. Your app runs on that simulator, not in a resized viewport or a picture of a phone frame.
Do I need a Mac or Xcode 27.1 to use it?
No. Running the Duo locally needs Xcode 27.1 on an Apple silicon Mac with macOS 26.6 or later. Here the browser is enough, on Windows or Linux included. Your app can be built in the cloud and run on the Duo too.
Is there an iPhone Duo emulator?
Not as such. Apple ships a simulator for the iPhone Duo, not an emulator: it runs iOS on the Mac rather than imitating the phone’s hardware, which is what most people mean when they search for an iPhone Duo emulator. VibeView streams that simulator online, so you can test your app on the iPhone Duo in a browser without installing Xcode.
Is there an iPhone Fold simulator?
Yes, under another name. Apple’s foldable iPhone is called the iPhone Duo, and its simulator ships with Xcode 27.1 and runs iOS 27.1. You can run it here in a browser tab, fold it to any angle and test your app on it, with no Mac.
How do I know if my app is optimized for iPhone Duo?
Run it on the iPhone Duo here, unfold the device and look at the inner screen. Apple’s preparation guide says apps built with the iOS 27.1 SDK or later are optimized for iPhone Duo and fill the whole inner display. It adds that there your app should look like a natural extension of its iPad layout and keep up with every size change a fold brings. If your app sits phone-sized in the middle, it was built with an older SDK. On the App Store, apps that submit iPhone Duo screenshots get a badge saying they are optimized for iPhone Duo.
Do I need to buy an iPhone Duo to test my app?
Not for layout. Here your app runs on Apple’s iPhone Duo simulator in a browser, where you can fold it to any angle and rotate it in each posture.
Can I set an exact hinge angle?
Yes. Pick Closed, Partial or Open, or turn on Set by angle and drag to any whole angle from 0 to 180 degrees. From the command line it is vibeview set-posture --angle 75, and an agent calls the set_posture tool with an angle.
Which screen do my taps go to?
The one the device is using. Closed, that is the cover screen; opened, the inner screen takes over and taps follow it. Part-way through a fold the device can keep the cover in use for a moment while the inner screen faces you, and taps on the unused screen are ignored until it switches.
Is the simulator pixel-identical to the hardware?
No, and it should not be read that way. It runs your app on Apple’s iPhone Duo simulator, on iOS 27.1, which is what layout, posture and orientation testing needs. Camera, sensors, real hinge feel, performance and battery are not simulated. Keep a pass on hardware before release.
Can someone without an account try my app on the Duo?
Yes. Choose the iPhone Duo as a share link’s device and the recipient opens your app on it in their browser. An embed key can include the Duo too, and adding ?posture=open to the iframe starts it unfolded.
