Apple unveiled the iPhone Duo on 9 September 2026: its first foldable device, 5.4 inches closed, 7.6 inches open. The reflex among web teams was immediate — a foldable, so two screen formats, so layouts to revisit.
That reflex is wrong, and that is what makes the subject interesting. Apple states plainly that both displays share the same aspect ratio, so content scales proportionally. The problem everyone is anticipating has been handled by the manufacturer. The one that remains has not.
What Apple settled, and is still blamed for
A book-style foldable normally poses a geometry problem: the inner screen tends towards square while the outer stays elongated, and an image framed for one crops badly on the other. That is the difficulty the industry has met since the first foldable, and the one habitually attributed to the iPhone Duo.
Apple chose the opposite: an identical aspect ratio on both sides. The consequence is real — a photograph, a video, a graphic composition carries from one screen to the other without distortion or cropping. On that specific point there is nothing to fix.
Which leaves untouched the problem nobody is looking at.
What actually breaks
In CSS units the device presents at roughly 466 × 678 points folded and 890 × 626 points unfolded — figures to treat as orders of magnitude, Safari’s actual viewport being smaller once the address bar is subtracted. Three things can be read in them.
- Folded, it is already wider than every iPhone. 466 points against 390 to 440 for current models. A site tuned to yesterday’s widths crosses a breakpoint before anyone has unfolded anything.
- Unfolding does not enlarge the screen, it pivots it. The aspect ratio is preserved but its orientation inverts: a viewport taller than it is wide becomes wider than it is tall. For a layout, that is the most abrupt change there is.
- It happens without a reload. This is the decisive point. Anything a page measures once, at load, becomes wrong the moment the device opens — and stays wrong.
The third point is what separates this case from every previous one. A screen rotation, a window resize on a desktop: browsers have signalled those for years, and serious sites handle them. Here the geometry changes in kind, not only in size.
Safari will not tell you it unfolded
A standard exists for this — viewport segments, which let a page know it is displayed on either side of a fold. It is implemented only in Chromium-based browsers. The iPhone Duo does not use one.
A site therefore cannot ask the browser where the fold is. All that remains is to observe what it sees: the viewport changed size, recompose. Which assumes never having frozen a measurement taken at load — and that is exactly what most sites do, without knowing it.
The right objective is not to recognise the iPhone Duo. It is to hold up at any width, without having to ask the browser where it stands.
Why a patch is not enough
A patch adjusts breakpoints: add 466 and 890 to the list of anticipated widths, retouch two margins, and the site more or less holds on today’s device. That settles the case, and only the case.
The flaw the iPhone Duo reveals is not a missing width. It is a way of designing: an experience built for a finite number of known formats, never for a device that changes shape while in use. The list of widths to anticipate will lengthen with every device, and the site will be late every time.
A UX redesign puts the question differently: do the visual hierarchy, the navigation and the conversion paths hold at whatever space is available, including space not yet seen? It is work on the rules of composition, not on a list of exceptions — and it makes the next device a non-event.
The precedent everyone has forgotten
The last break of this kind goes back to the iPhone X, in 2017, and its notch. It imposed a notion the web did not have: the safe area, the part of the screen where content can be placed without slipping under a hardware cut-out.
The sites that took it on board at the time never had to return to it. The others patched device by device for years. The difference was never about talent: it was about having treated the rule rather than the symptom.
What Maeliom offers
Maeliom runs a usability audit aimed at this precise point: how the site behaves at both geometries, whether conversion paths hold at the moment of change, and where something has been measured once and for all when it should not have been.
This is not a full redesign. It is a bounded check, run as a UX audit practice would run it, to find out whether the problem exists before visitors discover it on your behalf. And, where it does, to say whether a patch settles it or whether it reveals something else.
The first move costs nothing and needs no one: open your site in your browser’s developer tools, force a viewport of 466 × 678 and then 890 × 626, and resize from one to the other without reloading the page. What breaks at that moment is exactly what will break for your visitors.
If the result concerns you, write to us — or start with what the engagement covers.
And if the audit concludes that the site needs rebuilding, the question comes before the site: most rebuilds change nothing, for want of having settled what they were meant to say.
Common questions
How do you make a website work on the iPhone Duo?
By designing layouts that hold at any width and recompose when the window changes, without ever freezing a measurement taken at load time. Adding the device’s dimensions to a list of breakpoints fixes today’s case, not the next one.
Why can a website break on a foldable phone?
Because the window changes shape mid-session, without reloading: unfolding turns a tall window into a wide one. And Safari does not report the fold, as the corresponding standard only exists in Chromium-based browsers.
How can you test your site for the iPhone Duo without the device?
In the browser’s developer tools, force a window of about 466 × 678 points, then 890 × 626, and switch between them without reloading the page. Whatever breaks at that moment is what will break for your visitors.
Sources: Apple newsroom on the iPhone Duo (9 September 2026); a record of the viewport dimensions and of the missing fold-detection interface.