The very nature of the iPhone Duo raises numerous obvious questions about what it’s like to use. Does it not feel thick and heavy, awkward both to pocket and unpocket? Doesn’t the outer (cover) screen feel small and cramped, with an unfamiliar squat-rather-than-tall layout for UI controls in every app you use? Isn’t it weird that when you open it up to use the inner screen, that all the hardware buttons on the edges of the device are in the “wrong” places for a tablet? For anyone who’s gotten used to Face ID over the last decade, is it not frustrating to go back to Touch ID? And what about third-party apps that haven’t been updated to support the Duo’s novel displays — do they not suck to use?
Clearly, the point of a Duo review is to answer these questions, which really boil down to one question: How did Apple solve these problems?
The answer is: They didn’t.
All of these problems are real, and each of them detracts from the experience of using the Duo. Some of them have been mitigated through thoughtful design and clever engineering. Some of them might be solved in future iterations of the device. Some of them, though, I believe are endemic to the very idea of a foldable, and cannot be solved.
The Duo name is perfect. It truly is like having two devices in one. The outer device is, by far, the worst iPhone Apple has ever made. It’s a miserable fat little thing. The inner device is a splendid, joyful, beautiful tablet, with a UI that out-iPads the iPad. For me, by far, it’s my favorite tablet experience ever. I prefer it to any iPad or Kindle-like reader I’ve ever used.
So I’ll cut to the chase. The decision of whether you might want to buy a Duo is not easy, because only one of its two selves is good. You might be delighted, despite its clear compromises, if what you value most is a pocketable small tablet and are ambivalent about your iPhone. You might be endlessly frustrated if you love your iPhone, and use it extensively, often for quick interactions throughout the day, every day.
More Than Meets the EyeI was a kid when Transformers hit the toy market. I had a few — every boy my age did — but I was more of a GI Joe kid. It always bothered me that, as toys, Transformers were clearly compromised in both states. Folded up, they weren’t good cars / trucks / fighter jets. They had obvious seams and folds. In the cartoons — and the subsequent live action films decades later — the Transformers’ disguised states are seamless. In real life with the actual toys, the disguised states were about as convincing as a pair of Groucho glasses. A regular toy car looked like a real car, and stayed together no matter how hard you played with it. A Transformer car never quite looked like a real car and would come apart when played with. Unfolded, they looked like robots, yes, but they had obvious compromises. And it was kind of a pain folding them back into vehicles. My recollection is that we played with them a lot more as unfolded robots than as folded vehicles.
And that’s what they were. They weren’t vehicles that pretended to be robots. They were robots in disguise. The Duo isn’t really a phone. It’s a tablet in disguise. And in the same way that a true toy car was a better toy car than a folded-up Transformer-as-car could ever be, the Duo-as-phone is just not as good a phone as any regular iPhone. Honestly it’s not even close.
Consider if you could snap the Duo in half, leaving the smaller outer display as a standalone iPhone. Would anyone want an iPhone this shape and size? I think the answer is that zero people would want this. The iPhone Mini, back in 2020 and 2021 with the iPhone 12/13 generations, proved not to be popular enough for Apple to keep around. The iPhone Minis were a way better shape than the outer Duo. There’s a reason why the iPhone Air is not shaped like half a Duo — because the Duo shape stinks as an iPhone. And that’s only considering the hypothetical of a thin lightweight Duo snapped in half. In real life, with the actual Duo, when you use it folded up the device is twice as thick and twice as heavy. These Transformer watches were a fun way to smuggle a toy robot into school, but they were crummy watches. The iPhone Duo is a fun way to fit an entire iPad Mini–sized tablet into your pocket, but it’s a cumbersome phone.
It does not go into or out of my jeans pocket smoothly. Sometimes, in my pocket, it rotates 90 degrees, which is uncomfortable. Folded up it never stops feeling heavy. It is heavy, compared to other iPhones:
iPhoneWeight Duo254g 18 Pro Max249g 18 Pro211g 17177g Air165gIt’s technically only negligibly heavier than an 18 Pro Max, but because it has so much less surface area, it feels far more dense. If it did not unfold, no one would buy this.
But, of course, it does unfold. That’s the entire point. Unfolded, it not only no longer feels heavy, it feels featherweight light. It’s uncanny. An open iPhone Duo has a 7.6-inch display and the physical dimensions are 4.6 × 6.5 inches. An A17 Pro iPad Mini (the current model, but supposedly not for long) has an 8.3-inch display, measures 5.3 × 7.7 inches, and weighs 297g (that’s the cellular model’s weight, which is only fair). The iPad Mini has a slightly bigger screen but it’s heavier. In hand, I prefer the unfolded Duo over the iPad Mini as a tablet, in every single regard other than hardware button placement. (More on that below.)
You simply cannot have your cake and eat it too. The Duo allows you to take what is, in several ways, the best tablet Apple has ever made — and thus, the best tablet any company has ever made — fold it in half, and put it in your pocket to carry everywhere. While folded in half, you can use it as an entirely functional iPhone, but it’s by far the worst iPhone experience ever — frustrating, ungainly, and uncomfortable.
Using the Duo Closed, With the Outer DisplayEver since it was unveiled there’s been idle speculation that, while folded, the Duo’s design is biased against left-handed users. First, because the Touch ID side button is on the right. Second, because the Duo variant of iOS moves things like application toolbars and the home screen Dock to the right.
I am right-handed, but I’m a little bit on the ambidextrous spectrum. For example, I switched to using my mouse with my left hand around 1995, when I developed RSI in my right wrist, and I’ve used my mouse left-handed ever since. (But I use a MacBook trackpad with my right thumb.) I can shoot a basketball from close range with my left hand. So going into my Duo review, I thought I’d try to use my Duo as a pretend lefty. Turns out I didn’t have to pretend. I never realized this, but I naturally use my iPhone left-handed quite a bit throughout the day. For example, while brushing my teeth. I keep my iPhone in my right front pants pocket, but I often pick it up off my desk or kitchen counter and use it left-handed.
The Duo is not comfortable left-handed. The problem isn’t the Touch ID side button — I fixed that by registering my left index and middle fingers with the Touch ID sensor. The problem isn’t right-side bias for toolbars and the Dock in iOS Duo.1 That’s not great for left-handed use, but the truth is there’s a reachability problem no matter which single hand you try holding the Duo in. It’s better to hold it in your right hand than left, reachability-wise, but fundamentally it’s so wide that it’s a two-handed device even when being used folded.
No, the problem with holding the Duo in your left hand alone is that the bottom left corner of its D-shaped frame digs into your palm. When you hold it in your right hand, it’s a nice round corner in the meat of your thumb’s base. In your left, it’s a crisp sharp corner, and it doesn’t feel good.
When using the small outer display, everything on screen feels cramped. I don’t even like the home screen. Moving the Dock to the right side breaks 19 years of spatial memory for me.2 I keep reaching for Messages, Notes, and Safari down at the bottom of my screen, when now they’re over on the right. And they look weird too, because they’re smaller icons than the others on the home screen. Ostensibly the Dock is for your four most-used apps, but now they’re the smallest icons on your home screen? What sense does that make?
It’s such a little thing (no pun intended, I swear), but it exemplifies how many compromises Apple had to make for this small squat display.
Next, consider this screenshot from NetNewsWire:
What gets me here is the chevron “❮” back button being on the right. The iPhone’s back buttons have always been at the top left of the screen because iOS has always used a left-to-right column-view inspired spatial hierarchy. Craig Federighi just explained this spatial metaphor beautifully in a short YouTube interview a month ago. This metaphor is foundational to the iPhone experience. The back button is on the left because you go back to the left. Putting a button that takes you to the left on the right side of the screen just feels wrong. I think if I used an iPhone Duo every day for the next year (please no) I would still think this felt unnatural. It’s like having a turn signal stalk in your car that you move in the opposite direction that you turn the wheel. Now, it’s true that you can swipe from the left side of the screen to go back. You don’t have to use the “❮” button. But that button is there, in every single iPhone app that presents content in a hierarchy. And it’s always on the wrong side of the screen (unless you’re using an app on the left side of split screen multitasking — see below).
Here’s another example. Unforgetful is Marco Arment’s new reminders app. I like it a lot, and have been using it extensively since the summer. It’s properly updated to support the Duo UI layout. Here’s what it looks like when you’re creating a new task, normally:
But here’s what I saw over the weekend, when I was out running a Vonnegut errand, listening to The Vergecast:
I spent almost an entire minute trying to figure out how to save this task. I was about to text Arment with a bug report, that new tasks were unsaveable on the Duo, when I realized what happened. Because I had a Live Activity showing for the podcast I was listening to (in Arment’s Overcast, natch), the system’s time and circular status indicator were pushed down, reducing Unforgetful’s toolbar area, which meant the two buttons, “✕” and “✓” (for Close and Done, respectively), were collapsed into a single “···” overflow button. Tapping the dot-dot-dot button reveals them:
So the outer Duo display is so cramped when the keyboard is on screen that with a Live Activity showing, there is no longer room for a single pair of toolbar buttons. That turns a lot of one-tap actions into two-tap actions. And initially at least, it’s confusing. The whole point of Unforgetful is that it is not a complicated app. It really took me a minute to figure out that the Done button had moved into the “···” overflow menu.
One more examination of screen real estate, this time, with Messages, with the on-screen keyboard open. How much of the current conversation can you see?
The Duo outer display has only a smidgeon of real estate available for showing previous messages. It’s a bit like using an ancient BlackBerry. The Duo inner display in horizontal mode doesn’t show much more, but all you need to do to see more is rotate the device (which makes it easier for thumb-typing anyway).
Using the Duo Open, With the Inner DisplayOnce the Duo is unfolded and unlocked (more on that below), it’s a terrific experience. I absolutely love the nano-texture finish. I love how it looks, and I love how it feels.
At the outset of this review, I opened with a list of obvious problems for any foldable device. I omitted the one vexing problem that Apple has solved: annoyance at a visible crease. They solved it by applying this nano-texture finish (which apparently is an easily replaceable surface layer). But it’s not like this is a trade-off that makes the display look bad or feel weird. I’d love a display that looks and feels like this on my non-foldable iPhone 18 Pro. No glare, even in sunlight. It’s amazing. There’s no accounting for taste — some people love glossy reflective displays that draw glare from any and all light sources. Not me.
No foldable phone on the market had a matte inner display until the Duo. I suspect most of them will next year, and by 2028 all of them will.
I mentioned above how close the open Duo is to the size and weight of an iPad Mini (a little smaller in size, but 15 percent lighter in weight). It just feels like a great little tablet, and this general size class has always been great for reading. Most Kindles and other e-ink readers are about this same size. I love reading on the Duo inner screen, vertically.
The Duo is great horizontally too. One obvious use case is video. Watching video, it’s easy to forget it’s an iPhone, not an iPad. Here’s as good a place as any to mention that the Duo’s speakers are great. Loud and separated. It produces surprisingly good sound for such a thin device.
Held horizontally, the iPhone Duo supports side-by-side multitasking with two apps. The user interface for this feature is brilliant. It puts every idea Apple has tried on iPadOS for multitasking to shame.
From 2010 to 2015, the iPad behaved like a big iPhone, showing only one app at a time on screen. This was limiting, yes, but delightfully simple and obvious. In 2015 with iOS 9 (this was before Apple renamed the iPad’s variant of iOS to “iPadOS”), Apple introduced both Slide Over and Split View. Both of them stunk. They stunk so bad that if you gave them a ride, you’d have to sell your car afterward. They were confusing and unintuitive. Slide Over in particular was often invoked accidentally and users couldn’t figure out how to get rid of it.
Even the newest iPads of the time (iPad Air 2, iPad Mini 4) still had Home buttons — the all-screen design without a Home button wouldn’t arrive until the iPhone X debuted in 2017, and it didn’t arrive for iPads until the late 2018 iPads Pro. The Home button was the key to all iOS interaction at the time. To launch an app, you tapped its icon on your home screen. To go back to your home screen, you clicked the Home button. You double-clicked the Home button to enter the app switcher. If you think about it, you can see how the Home-button-centric iPad hardware was incompatible with the idea of split-screen multitasking. Once you have two apps on screen at the same time, how can you control them with just one clickable Home button? What if you had, say, Notes on the left and Safari on the right, and you wanted to close Notes and replace it with Mail, while keeping Safari open on the right? How could the system know which one you wanted to close when you clicked the one Home button? The answer is it couldn’t. So Apple devised all sorts of other convoluted ways to manage this. I don’t even remember how it worked except that it was confusing and frustrating. Re-reading this old iPad developer documentation makes it seem even more unintuitive than I remember.
I was about to quip that whoever at Apple designed and approved of these multitasking UIs set the entire iPad platform back by a decade. Then I realized that, actually, it was more than a decade. The iPhone Duo is debuting 11 years after iOS 9’s terrible iPad multitasking, and only now has Apple designed and implemented a split-screen multitasking interface that is actually good. Split screen on the Duo is intuitive, natural, useful, and mostly obvious. In addition to all those accolades regarding how you purposely invoke and use it, it also is an interface that you seem unlikely ever to get into accidentally. Comparing the multitasking UI on the Duo to the iPad is like comparing the Mac to Windows — one is insanely great, the other a dog wearing a necktie pretending to be a person. Apple should throw out iPadOS’s multitasking interface and switch to this one. Honestly I’d prefer if they just threw out iPadOS and went back to running iOS — this new version of iOS created for the Duo — on iPads. The Duo flavor of iOS is a better tablet OS than iPadOS, Apple’s dedicated tablet OS.
On the Duo, split screen is only available when the device is horizontal. It’s always split 50-50. Each side of the screen gets an app that is basically the size of an app open on the outer display. Elegant. To move an app into split view, you drag the home indicator up from the bottom of the screen — the same gesture that takes you back to the home screen. But instead of letting go, you keep dragging. You get this:
Those shelves on the left and right are drop targets. Drag and drop the current app to either side to put it there and enter split screen. The other side of the display just shows you a single-screen home screen:
To open an app on that second screen, you just tap it. There is no step 2. Once you enter split screen mode, it’s like having two closed Duos side-by-side, except the left-side one is a reverse D shape. When the left side is open you can see that the Duo toolbar/Dock bias is not “put it on the right side”. It’s “put it on the outer side”. It just so happens that on the outer display, the right side is the outer side (with rounded corners, away from the spine). Open a second app, and that app’s toolbar will go on the left, if the app is on the left:
Each side of split screen acts like its own iPhone Duo. Drag up from the bottom of a side and you can go back to the home screen on that side. Or, as shown above, you can enter the multitasking switcher interface on that side — and it’s smart enough not to show you the app that is already open on the other side. Drag up from the bottom center and you return to the full-screen home screen or full-screen app switcher. Whatever you think ought to work, probably works. That’s intuitive design.
There is more to explore and think about here. These are not “windows”. But you can open the same app on both sides, like to show two Safari pages side-by-side. What this split screen UI gets fundamentally right is that it works exactly like using the iPhone for one-app-at-a-time launching and switching. The iPad’s original split-screen sin was trying to implement multiple apps on screen at the same time when the iPad still used a hardware Home button. With the modern iOS UI, where the physical Home button has been replaced by virtual on-screen home indicator bars, you can go from one home indicator (when there’s only one full-screen app) to three: one for the app on the left, one for the app on the right, and a third in the center to control them both as a pair. It’s so brilliant that most users won’t notice that there’s anything clever about the design at all. They’ll just use it. That’s the highest praise for an interaction design like this. It seems so obvious that it doesn’t seem designed at all.
Ironically, because iPhone Duo is not called an “iPad”, it gets to be what the iPad should’ve been all along.
The biggest problem I have with using the Duo on the inner display is an incorrect intuition that, after a full week of use, I am only now starting to break. What do you do when you’re done with a book for now? You close it. So what do I do when I’m done using the iPhone Duo, unfolded, before putting it in my pocket? I close it. But that doesn’t lock the Duo. It just swit