> I expect that most apps will look rather broken on release, but it will be smoothed out eventually.
I don’t think it'll be "most apps".
Apple all but told developers in June [1] to update their apps not to assume a fixed screen size.
One of the apps Apple's engineers demonstrate new features was called Origami [2]. When I watched the video, it seemed pretty clear: a device that folds was in our future.
If you’re a developer that's kept up with the latest iOS developments, you'll be in good shape for the Duo.
But if you're up to your eyeballs in technical debt using deprecated frameworks and APIs… it's probably gonna be a while for you.
Apps that support iPad are 95% fine unless you do crazy custom things (which Apple has been telling developers for decades now that they shouldn’t do), and apps that are phone only are letterboxed, but still entirely usable.
How many customers do you expect to be running on Duo for the first year of its existence?
I’d be surprised if it was >0.01% for anyone. Apple wants you to drop everything to support all the bells and whistles for their new device, but even if you take 3 months to fix minor layout bugs, I don’t think it’s that big of a deal.
I have friends who dropped everything to support the Vision Pro, and I don’t think any of them felt like it was worth it in retrospect. Even the ones that got featured by Apple as a result didn’t see more than a few thousand downloads.
> I have friends who dropped everything to support the Vision Pro, and I don’t think any of them felt like it was worth it in retrospect. Even the ones that got featured by Apple as a result didn’t see more than a few thousand downloads.
They should remember that they got quite a bit of social capital within Apple by doing that and hopefully they're keeping those relationships warm. But yeah Vision Pro hasn't turned out to be a big ecosystem so far.
Usually just compiling with the new SDK will get apps basic support if they have been following Apple standards.
> I have friends who dropped everything to support the Vision Pro
The VP was a niche device for a niche market. Phones are not that. I think the Duo will do very well. The one knock are the cameras do not match the Pro. I don't think will care though.
> How many customers do you expect to be running on Duo for the first year of its existence?
I’d be surprised if it was >0.01% for anyone.
How do you figure? Assume the average Apple cell phone replacement cycle is somewhere between 3 and 4 years. At the longer end, you’d need the sell-through rate of the Duo compared to other phones to be less than 0.04% to hit your number. We know from the Mini and other phones that Apple tends to avoid designs that it expects to have less than a 5% sell rate, two orders of magnitude higher. Even if you assume they’re aiming for 5% of dollars instead of units, and you take into account the non-Apple market (which certainly should not be unit-weighted for folks thinking about app revenue), you’re off by well over an order of magnitude.
Why? If you’re spending 2000 hours a year servicing your current customers, surely it’s worth 20 hours to add on 1%, even ignoring that that 1% is probably more valuable than your average customer, and the halo effect of giving a good experience to existing users migrating devices.
Although maybe they should because someone willing to buy a $2000 phone on launch is probably more willing to buy a lot more things versus someone who keeps phones a long time.
Apple does many crazy custom things in their own apps. Their advice is not sacrosanct. It just means you must prepare for less notice than they had if you want to compete with the frontier UI aspects that Apple apps achieve.
Fired it up to check my own app (RunnerCast) and it looks fine. The Liquid Glass menu moves from the bottom to the right side automatically both on the inner and outer screens. If you already had a layout that worked for iOS and iPadOS, things adapt fine to the inside screen and when you go split screen with two apps, the layout adapts nicely. I don't think I'll need to do a thing.
I've also noticed a flurry of recent app updates from some of the bigger apps (MLB, NYTimes, etc.) to switch to the Liquid Glass menu which I assume Apple strongly suggested they do prior to the Duo launch.
It’s really interesting to note how the bigger apps deferred adopting Liquid Glass altogether until iOS 26 is out for almost a year. Do most developers making large apps also loathe it? Do they have in-house designers telling them not to adopt it?
Unless Apple uses their stick (whip, or whatever else) to drive the developer community, I bet iOS will experience the same app fragmentation as Android does regarding various form factors, more so than between iPad, iPhone and iWatch already.
Tongue half in cheek, my point is that agents may be unreliable with fresh libraries.
It looks like there are some fun edge cases too:
> A reserved region can be active or inactive. For example, a reserved region that represents the fold is active when iPhone Duo is partially open, but inactive when it is fully open.
Note: I'm scrubbing it against the final 27.1 beta SDK as I type this, so it's likely that its Duo knowledge will get an update within the next few hours.
Fun fact, I’ve now worked on the surface duo (technically the windows version not the android version) and the iPhone duo.
I thought the ideas of the surface duo were great and I’m super excited to see them evolved and shipped in a product that I think a lot of people are going to love.
They finally released the full experience a few months back. I think their original excuse (years ago) was that 'people take photos on iPhone so iPad is unnecessary for Instagram'.
Most apps people actually use will look fine because there's a team of mobile devs in all big companies who get paid to keep up with Apple breaking their apps every year with their 'updates' (among other things).
I mean, don't expect advanced features like consistent smooth scrolling, non-broken UI, absence of animation flickers, cloud sync that works consistently even for paid apps developed by Apple or anybody else but other than that :)
This is the first time we get an iPhone skew that is significantly different and with no sales track record.
For instance, very few company bothered to do anything for the Vision Pro. Now we'll see if Google or Microsoft for instance see the iPhone Duo as a main line product or an exotic offshoot that needs to prove itself before any money is spent on it.
Apple’s Developer Documentation is historically pretty terrible. So I’d be curious to see if they stepped it up for the agent instructions for the new API’s.
Apple's current docs suck, and they have, for a long time (SwiftUI was so bad, that someone came up with this[0], and it was a lifesaver).
But I'm old enough to remember Inside Macintosh[1], and that was a thing of beauty.
Apple used to take technical documentation very seriously. Many of their technical writers had better tech chops, than the engineers making the stuff they wrote about.
I think this is my main hesitation with picking up the Duo on the first release. I have no doubt the build quality is exceptional, but the chance that the apps I use are not well optimized for this new form factor is pretty high in the first year of its release.
I don't think they won't work, but I anticipate oddities to appear for a while, especially for older applications.
This is my feeling too. It looks great - I think I might pick one up. But I’m going to give apple a few years to iron out the bugs first. Version 3 of the duo will be a much better product than version 1.
I’m not sure about this, we already support resizing on our app for a while now because of our iPad/mac catalyst version, so I fail to see how different it would be on the Duo.
I assume other apps will have have the same, since our team is super small compared to everyone else.
But will you gain anything by building for it? Will you see noticeably more users or people choosing another alternative because you didn't specifically building the app for Duo? At least if it doesn't outright break.
We're not talking about 0/1 here. There's making sure the app works and looks ok on the Duo and then there's building out Duo specific features. The works/looks ok is generally pretty easy with new devices. Just build with the new SDK and fix places where the app wasn't doing something likely already suggested by Apple. A big one will be safe areas which people often ignored except on the top and bottom.
I would get a little bit of joy if a duo user noticed the effort I put into making my app work well on their device. Why put effort into anything? Your take is bordering dangerously on cynicism. :)
You could say this about every QoL feature though. That’s not a reason to not do it though, it adds up and at some point other apps that do bother to make their apps as good as possible will become more popular than yours.
Duo users also likely have disposable income to spend on in app purchases, maybe click on ads to purchase things, and other monetization. So I do think it's worth building for it.
Will you see noticeably more users or people choosing another alternative because you didn't specifically building the app for Duo?
I haven't done iOS development in a long time, but my understanding is that if your iPhone app is designed well and uses all of Apple's recommended methods, adjusting for different screen sizes and orientations is fairly easy.
If you decided to go cheap/easy/dumb from the outset, then you made your bed, and now you get to lie in it.
Not really. It's an iPad + iPhone. That's hardly exotic. Both of those product categories sell very well. People who own an iPad mini and an iPhone have every reason to consider this for the merged cost.
It is indeed a niche product. Its price reflects the sales expectations of Apple.
But its form factor has been validated for almost a decade now from other manufacturers. So iPhone Duo will do fine. It will not surpass a slab iPhone but fine.
Vision Pro was a completely new beast, the hardware was not there, the market was not there.
It's worth noting that "niche" in this case means ~10M in its first year, comparted to an estimated 250M Apple smartphone shipments in 2027. So far, Apple has sold ~600K Vision Pro in total.
Also, supporting Duo is not an enormous lift if you're already supporting resizable windows, as developers are required to do for OS 27.
Yeah the market had shown that anything bulkier/heavier than a pair of regular glasses is not acceptable. Not sure why apple released it unless it is a glorified dev kit that would allow devs imagine a use case for a product that is 10 years away.
> I know exactly one person who has a foldable phone and I live in sf.
If we're comparing anecdotes, when I lived in the states far from sf many tech people I knew had folding phones. They loved them and I was curious, but I like iOS.
My only concern is that they'll sell out so quickly for so long that I'll have to wait for the iPhone Duo Two-o because they won't be easy to get until like May 2027.
Developer here. Apple often rejects app submissions if the app doesn't look optimized for some iPhone device or iPad device. So won't be surprised if they reject new apps and updates for not being optimized for the Duo. This could be their way of getting developers to comply.
That seems like a tough road. They've never been able to enforce that iPhone app makers build an iPad-compatible version or vice versa, and this looks exactly like that scenario.
It's mostly enforced, the only exception being apps with a legitimate iPhone-only hardware dependency.
iPhone apps must function on iPad in iPhone-compatibility mode, apps must support window resizability as of OS 27, and apps can't detect iPad and refuse to run. And I don't think this is new, but setting the target to iPhone-only doesn't prevent iPhone apps from running on iPad.
I really wanted to use it as my primary computing display, but as is almost always the case with Apple, the amazing hardware was hamstrung by the crippled OS.
Even just being able to use it as a generic display i.e. with a Nintendo Switch would have been amazing.
It really feels quite irrelevant. Also, the amount of work to support this with zero support from Apple since WWDC is just absurd. And even if one does the work, Apple will just sherlock the cool features into their apps.
And when did Apple decide to grace us with tools to support the Duo? Yeah, 3 hours ago. This should've been out in June so they can also get the feedback about all the silly design choices the Duo brings (and the bugs in that simulator). Too bad I can't just send them an invoice for all the wasted time.
Waiting for my coding agent to have zero idea what I mean when I say build for iPhone duo (due to knowledge cutoffs in pre-training; happened when Liquid Glass came out previously).
I coincidentally asked Gemini a question about the iPhone Duo a few hours ago and, while it seemed to understand that it's a folding phone, it confidently hallucinated that in "tent" pose, there would be a display visible from both sides. In reality, only one side in this pose is the display, the other side is just back glass with the large cameras.
I expect that most apps will look rather broken on release, but it will be smoothed out eventually.
I don’t think it'll be "most apps".
Apple all but told developers in June [1] to update their apps not to assume a fixed screen size.
One of the apps Apple's engineers demonstrate new features was called Origami [2]. When I watched the video, it seemed pretty clear: a device that folds was in our future.
If you’re a developer that's kept up with the latest iOS developments, you'll be in good shape for the Duo.
But if you're up to your eyeballs in technical debt using deprecated frameworks and APIs… it's probably gonna be a while for you.
[1]: https://developer.apple.com/videos/play/wwdc2026/278
[2]: "Modernize your UIKit app" — https://en.wikipedia.org/wiki/Origami
How many customers do you expect to be running on Duo for the first year of its existence?
I’d be surprised if it was >0.01% for anyone. Apple wants you to drop everything to support all the bells and whistles for their new device, but even if you take 3 months to fix minor layout bugs, I don’t think it’s that big of a deal.
I have friends who dropped everything to support the Vision Pro, and I don’t think any of them felt like it was worth it in retrospect. Even the ones that got featured by Apple as a result didn’t see more than a few thousand downloads.
They should remember that they got quite a bit of social capital within Apple by doing that and hopefully they're keeping those relationships warm. But yeah Vision Pro hasn't turned out to be a big ecosystem so far.
That social capital and $5 will buy me a cup of coffee.
> I have friends who dropped everything to support the Vision Pro
The VP was a niche device for a niche market. Phones are not that. I think the Duo will do very well. The one knock are the cameras do not match the Pro. I don't think will care though.
How do you figure? Assume the average Apple cell phone replacement cycle is somewhere between 3 and 4 years. At the longer end, you’d need the sell-through rate of the Duo compared to other phones to be less than 0.04% to hit your number. We know from the Mini and other phones that Apple tends to avoid designs that it expects to have less than a 5% sell rate, two orders of magnitude higher. Even if you assume they’re aiming for 5% of dollars instead of units, and you take into account the non-Apple market (which certainly should not be unit-weighted for folks thinking about app revenue), you’re off by well over an order of magnitude.
I've also noticed a flurry of recent app updates from some of the bigger apps (MLB, NYTimes, etc.) to switch to the Liquid Glass menu which I assume Apple strongly suggested they do prior to the Duo launch.
Interestingly, Instagram decided to implement a custom liquid-glass like tab bar which surely now turns to be a PITA.
Tongue half in cheek, my point is that agents may be unreliable with fresh libraries.
It looks like there are some fun edge cases too:
> A reserved region can be active or inactive. For example, a reserved region that represents the fold is active when iPhone Duo is partially open, but inactive when it is fully open.
source: https://developer.apple.com/documentation/technologyoverview...
You may find Axiom (my FOSS project, updated for iPhone Duo) helpful. https://charleswiltgen.github.io/Axiom/
Note: I'm scrubbing it against the final 27.1 beta SDK as I type this, so it's likely that its Duo knowledge will get an update within the next few hours.
I thought the ideas of the surface duo were great and I’m super excited to see them evolved and shipped in a product that I think a lot of people are going to love.
Sadly, many apps will continue to look rather broken.
There are still thousands of apps that still look wrong on iPad 16 years after its release, even with the 2x button pushed, for no good reason.
I think I heard that Instygram only recently figured it out.
I mean, don't expect advanced features like consistent smooth scrolling, non-broken UI, absence of animation flickers, cloud sync that works consistently even for paid apps developed by Apple or anybody else but other than that :)
For instance, very few company bothered to do anything for the Vision Pro. Now we'll see if Google or Microsoft for instance see the iPhone Duo as a main line product or an exotic offshoot that needs to prove itself before any money is spent on it.
My brain must have blocked out the 'cadence' (oh the corpo speak!) of corporate dev out of self preservation.
Depends on how far back you go.
Apple's current docs suck, and they have, for a long time (SwiftUI was so bad, that someone came up with this[0], and it was a lifesaver).
But I'm old enough to remember Inside Macintosh[1], and that was a thing of beauty.
Apple used to take technical documentation very seriously. Many of their technical writers had better tech chops, than the engineers making the stuff they wrote about.
[0] https://swiftui-lab.com
[1] https://vintageapple.org/inside_o/
Historically it was very good. Back when I was writing Mac and iOS apps in objective-c, Apple's docs were some of the best.
I don't think they won't work, but I anticipate oddities to appear for a while, especially for older applications.
I assume other apps will have have the same, since our team is super small compared to everyone else.
Here are some screenshots from getting my own app compiled, if anyone is interested:
https://bsky.app/profile/cameronbanga.com/post/3mvsrxk5q7b2j
https://bsky.app/profile/cameronbanga.com/post/3mvss5wmxej2l
We're not talking about 0/1 here. There's making sure the app works and looks ok on the Duo and then there's building out Duo specific features. The works/looks ok is generally pretty easy with new devices. Just build with the new SDK and fix places where the app wasn't doing something likely already suggested by Apple. A big one will be safe areas which people often ignored except on the top and bottom.
As a professional programmer, it at least gratifies me to know this is the attitude I'm competing against.
I'm not an iOS developer, never made an app at all, I asked because I'm curious. What is it really to gain?
Nothing ventured, nothing gained.
Will you see noticeably more users or people choosing another alternative because you didn't specifically building the app for Duo?
I haven't done iOS development in a long time, but my understanding is that if your iPhone app is designed well and uses all of Apple's recommended methods, adjusting for different screen sizes and orientations is fairly easy.
If you decided to go cheap/easy/dumb from the outset, then you made your bed, and now you get to lie in it.
But its form factor has been validated for almost a decade now from other manufacturers. So iPhone Duo will do fine. It will not surpass a slab iPhone but fine.
Vision Pro was a completely new beast, the hardware was not there, the market was not there.
It's worth noting that "niche" in this case means ~10M in its first year, comparted to an estimated 250M Apple smartphone shipments in 2027. So far, Apple has sold ~600K Vision Pro in total.
Also, supporting Duo is not an enormous lift if you're already supporting resizable windows, as developers are required to do for OS 27.
And that means nothing. Because other manufacturers are not doing well either.
I’m not doubting that there’s demand for it but I wonder who/where?
If we're comparing anecdotes, when I lived in the states far from sf many tech people I knew had folding phones. They loved them and I was curious, but I like iOS.
I spend a lot of time in hospitals, and I see doctors with them.
That may also explain why Apple isn't too worried about the price.
People famously said that of the first iPhone, expensive at the time.
Then about the $1k iPhone X.
Apple have made phones a fashion accessory and status symbol. I won’t be surprised if the Duo sells extreme well, even by iPhone standards.
iPhone apps must function on iPad in iPhone-compatibility mode, apps must support window resizability as of OS 27, and apps can't detect iPad and refuse to run. And I don't think this is new, but setting the target to iPhone-only doesn't prevent iPhone apps from running on iPad.
I really wanted to use it as my primary computing display, but as is almost always the case with Apple, the amazing hardware was hamstrung by the crippled OS.
Even just being able to use it as a generic display i.e. with a Nintendo Switch would have been amazing.
Resources:
https://developer.apple.com/search/?q=iphone%20duo
Axiom: https://charleswiltgen.github.io/Axiom/ (my FOSS project, updated for iPhone Duo)