Xcode 27.1 Beta Release Notes
developer.apple.com139 points by CameronBanga 15 hours ago
139 points by CameronBanga 15 hours ago
Finally! So we have a little over a month between getting the simulator and first customers running our apps in Duo.
I expect that most apps will look rather broken on release, but it will be smoothed out eventually.
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.
Because Apple has always treated its developers so well!
Vision Pro will be cancelled at some point, it’s just nowhere near popular enough and never will be - the air has gone out of that VR bubble.
I wouldn’t be surprised if duo is also cancelled because it is another copycat move which is not central to Apples business and will not be mass market.
It's going to be mass market and I wouldn't be surprised if it sells out on launch day in the US.
Based on what? At that price tag, I doubt it will be mass market, but perhaps I’m wrong.
> a bit of social capital within Apple by doing that and hopefully they're keeping those relationships warm
That social capital and $5 will buy me a cup of coffee.
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.
> apps that are phone only are letterboxed, but still entirely usable
How is that possible? iPhones have had varying screen sizes for more than a decade, how could any app still have a fixed size?
There are many. We have an online supermarket with an app (Picnic) who don't support iPad, don't support landscape, don't support dark mode, etc.
I bet it's due to product managers not caring about those.
Because despite Apple having clear guidelines a huge number of developers think their 'custom UI' is what customers really want. When they don't. The best apps use system components and follow the HIG. Always have, always will. Your custom tab bar is stupid.
> 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.
If he is off by an order of magnitude and it's 0.1% still no developer (unless a fanboy) should bother
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.
> some of the bigger apps to switch to the Liquid Glass
Interestingly, Instagram decided to implement a custom liquid-glass like tab bar which surely now turns to be a PITA.
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?
> 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
Also, every iPad has a full window server. So any app that was available for iPad, should've been resizable in any shape.
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.
"You are a experienced iOS Software Engineer, your task is to migrate this application to the iPhone Duo layout...
“Here is your iOS app migrated to Surface Duo…”
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...
> Tongue half in cheek, my point is that agents may be unreliable with fresh libraries.
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.
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.
I expect that most apps will look rather broken on release, but it will be smoothed out eventually.
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.
Instagram released a Reels-first iPad app that is much, much worse than the old iPhone-on-iPad app.
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'.
To me that's said more about Instagram than the feasibility of building an app for a tablet.
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.
In plenty of big companies one month is not even enough time to get a new release into production, let alone test and fix the layouts.
You're right.
My brain must have blocked out the 'cadence' (oh the corpo speak!) of corporate dev out of self preservation.
None seem to be working at Meta.
How many years has it been for them to release an upscaled (zero extra features!) version of instagram and whatsapp for iPad?
Two of the most used apps in the world
I've been testing with Xcode 27.1 on the Duo simulator and I was pleasantly surprised that nearly everything worked well, untouched. The main thing I need a real device for is knowing which buttons are easier or harder to press on the right edge, but using modern UIKit this was not that difficult. That, and taking advantage of the left/right inner display content areas.
Apple also bundles a /uikit-app-modernization skill which should help with adopting layouts to iPhone Duo.
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.
> historically
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.
I really wish they still did, instead of focusing so much on trying to make it simple and obvious like in SwiftUI. Objective-C was a pinnacle of computing, and ever since Swift they've been devolving into the pursuit of oversimplifying and abstracting away the details such that they don't even feel necessary to teach anymore, even though as a new developer, I WANT TO KNOW THEM.
> Apple’s Developer Documentation is historically pretty terrible.
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 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.
The small screen is so small they had to move controls to the right, I would expect glitches because of that, especially for custom controls.
Apps not rebuilt with the latest SDK will display in pillar-boxes mode, centred on the screen.
Looks like Safari 27.1 on Duo ships without support for CSS viewport segments and any other CSS or JS to handle foldables.
I'm not a webdev, is that surprising? Or is it more something that you would have wanted or expected?
Certainly, these aren't new standards and have been available on Android. We like to offer a split page when a foldable is used in a book pose and avoid having anything (especially interactive elements) in the middle.
Now available for testing apps on the iPhone Duo!
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
I presume this Xcode 27.1 beta will not want to launch on our Mavericks Forever, the last Mac OS we actually like and use.
I started adding support for iPhone Duo in some of my apps. Here's an example of some of the work required https://mastodon.social/@simsaens/117296064810231465 — all my apps are hobby apps. Even though they all support iPad / resizability, it's still a large amount of work
Thanks for Axiom, looks useful. Does it already cover the new 27.1 beta APIs?
I'm just gonna ignore this thing and continue as if it never existed. Worked with Vision Pro that no body uses and will work with this.
I'm not fangirling over it, but comparing it to Vision Pro is ridiculous.
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.
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. :)
No, it's based on pragmatism. Every feature is a cost/benefit tradeoff. You didn't answer the question: would it be worth it?
> But will you gain anything by building for it?
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 user, this attitude makes me sad.
As a professional programmer, it at least gratifies me to know this is the attitude I'm competing against.
Thanks for the backhanded compliment, very mature..
I'm not an iOS developer, never made an app at all, I asked because I'm curious. What is it really to gain?
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.
Can two people use opposite sides while in tent mode? Because that makes for some fun in-person games.
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.
But will you gain anything by building for it?
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.
It is exotic, and bring only a little to the table for a stiff price increase.
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.
Exactly. Maybe not v1, but the Duo will likely lead me to not buy another iPad.
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 is indeed a niche product.
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.
The form factor of Vision Pro has also been validated for a decade from other manufacturers.
And that means nothing. Because other manufacturers are not doing well either.
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. I’ve never even considered getting one and I like new tech.
I’m not doubting that there’s demand for it but I wonder who/where?
> 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.
I’m not doubting that there’s demand for it but I wonder who/where?
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.
The price, hardware, and market was not there for the Vision Pro. There was no reason to buy a VR headset that couldn’t play games.
> Its price reflects the sales expectations of Apple.
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.
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 had the 1st-gen Vision Pro, and then sold it.
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.
> Also, the amount of work to support this with zero support from Apple since WWDC is just absurd.
Resources:
https://developer.apple.com/search/?q=iphone%20duo
Axiom: https://charleswiltgen.github.io/Axiom/ (my FOSS project, updated for iPhone Duo)
What is your point? That they eventually released something? The simulator came out today... on Friday afternoon lol
I don't understand what you mean by "eventually" when you can't even pre-order it yet.
Why does it feel irrelevant? And what kind of support should Apple be providing beyond releasing Xcode and an iPhone Duo simulator?
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.
Honestly if they were really serious about this they would have released this back in December. Shame. Steve Jobs is rolling in his grave!!
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.