Updated for iOS 27.1 Safari on the iPhone Duo
iPhone Duo Simulator for Websites
Paste your URL. We load it in a real headless browser on the folded 5.4″ screen and the unfolded 7.6″ screen, flag what breaks at the center crease and hand you HD screenshots of both.
What breaks on the iPhone Duo
Apple's first foldable gives Safari two shapes no other iPhone has. Most sites built for the iPhone 18 still have at least one of these problems.
Narrower than any modern iPhone
Folded, your page gets 382 px. That's 20 px less than an iPhone 18 Pro (402 px), so fixed-width cards, tables and code blocks that fit everywhere else start scrolling sideways.
An 84pt Safari column on the right
On the outer screen, iOS 27 moves the clock, front camera and Safari buttons into a vertical strip on the right edge. Full-width sticky headers stop short against it, and Safari ignores theme-color for that strip.
A crease at x = 475.5 px
Unfolded, the fold runs down the center of the page. Centered hero headlines and CTA buttons are split in half, which looks wrong when the phone is propped open.
Tablet breakpoints on a phone
Unfolded landscape is 951 px wide but only about 543 px tall. Layouts switch to their tablet or desktop design, and tall hero sections push the call to action below the fold.
How the iPhone Duo simulator works
- 01
Paste a URL
Any public page: your homepage, a pricing page, a checkout or a blog post.
- 02
We render it twice
Headless Chromium with an iOS 27.1 Safari user agent, touch enabled and a device pixel ratio of 3, at the folded and unfolded Safari viewports.
- 03
Get screenshots and fixes
Both screenshots in an iPhone Duo frame, a Duo score out of 100, and every overflow, clipped bar and crease collision we found.
iPhone Duo screen sizes at a glance
| Folded (outer) | Unfolded (inner) | |
|---|---|---|
| Screen size | 5.4″ | 7.6″ |
| Resolution | 1398 × 2034 px, 460 ppi | 2670 × 1878 px, 430 ppi |
| Screen in points | 466 × 678 pt | 951 × 669 pt |
| Safari viewport (portrait) | 382 × 580 CSS px | 669 × 825 CSS px |
| Safari viewport (landscape) | 678 × 340 CSS px | 951 × 543 CSS px |
iPhone Duo simulator, emulator or the real phone?
Xcode's iPhone Duo simulator is the most accurate option, but it needs a Mac, a multi-gigabyte download and it is slow to boot. Chrome DevTools can emulate any width, but it won't show the Safari column on the right or tell you where the crease falls. The phone itself starts at $1,999.
DuoBreak sits in between: it works from any browser, takes about ten seconds, and checks the iPhone Duo problems for you instead of leaving you to spot them by eye.
Frequently asked questions
Is there an iPhone Duo simulator for websites?
Yes. DuoBreak is an online iPhone Duo simulator for websites: paste a URL and it loads the page in a real headless browser at the iPhone Duo's measured Safari widths, 382 CSS px on the folded outer screen and 951 CSS px on the unfolded inner screen, then returns screenshots and a list of layout problems. You don't need a Mac, Xcode or the phone.
What is the iPhone Duo's screen size?
The iPhone Duo has a 5.4″ outer display (1398 × 2034 pixels, 460 ppi) and a 7.6″ inner folding display (2670 × 1878 pixels, 430 ppi). Apple measures them as 5.36″ and 7.58″ as standard rectangles.
What is the iPhone Duo's viewport width in Safari?
Folded, Safari gives a web page 382 CSS px of width, because iOS 27 keeps an 84pt column for the camera, status and Safari buttons on the right of the 466 × 678 pt screen. Unfolded in landscape the page is 951 CSS px wide. Device pixel ratio is 3.
Does the iPhone Duo crease affect websites?
The crease is barely visible, but it runs down the exact center of the unfolded screen at x = 475.5 CSS px. Headlines, buttons and form fields centered on the page sit right on the fold, which is where the hinge flexes and where the screen is split when the phone is half-open. DuoBreak lists every heading, link and button that straddles it.
Is an iPhone Duo emulator the same as a simulator?
For web testing, people use the words interchangeably. Apple's iPhone Duo simulator in Xcode runs native apps on a Mac. A browser-based emulator like DuoBreak or Chrome DevTools only changes the viewport size and user agent. DuoBreak goes further by measuring overflow, the right-side Safari column and the center crease for you.
How much does a check cost?
Each check is $1, paid once through Stripe Checkout. There is no account or subscription. You get both screenshots, a Duo score out of 100 and the list of issues.