Free · No signup · About 30 seconds
Will your site hold up on the iPhone Duo?
A free iPhone Duo website checker. Paste a URL. We load it at the four screen sizes Safari gives a page on the Duo and tell you what breaks, in plain English, with the fix.
Outer, in Safari
382 pt wide
Outer, full width
466 pt wide
What it is
Why check a site for the iPhone Duo at all?
FoldReady renders your page at the sizes the iPhone Duo actually gives Safari, which are not the sizes of any phone or tablet you have tested on, and scores how well it adapts.
The Duo has two screens and four common page shapes. The outer screen loses an 84 pt strip to Safari's controls. The inner screen is wide when you hold it one way and tall when you turn it. A layout that was fine on a phone can scroll sideways at 951 pt, or hide a button under the rail at 382.
Checking it takes a URL and half a minute, and fixing what it finds before launch week is cheaper than fixing it after.
What we check
Five checks, scored per screen.
Each screen starts at 100. A critical finding costs 15 points, a warning costs 5, and no one check can take more than 30. Your overall score is your worst screen, and a screen passes when it loads and has no critical finding.
The vh and pinned-element checks are heuristics and are labelled that way. Fold transitions arrive in a later release.
The page scrolls sideways
Something is wider than the screen, so people have to drag the page left and right to read it.
Viewport tag missing or locked
Without a proper viewport tag Safari lays the page out as a desktop page and shrinks it, or the page is pinned to a width that fits neither screen.
Pinned element under the Safari side rail
On the outer screen Safari keeps an 84 pt rail on the right. Fixed or sticky controls that reach into it can end up covered.
Heights set in vh
vh is measured with Safari’s toolbar retracted, so a full-height section is taller than the visible area while the bars are showing.
Tap targets under 44 pt
Small buttons and links are hard to hit with a thumb, and the Duo’s narrow outer screen makes it worse.
FAQ
Frequently asked questions
Something the checker got wrong, or a question we have not answered? Tell us and we will look at the page itself.
Contact usWhat is FoldReady?
FoldReady is a free checker that loads a public web page at the four screen sizes Safari gives a page on the iPhone Duo, then reports what breaks: sideways scrolling, tap targets too small for a thumb, pinned controls hidden under Safari’s side rail, heights set in vh, and a missing or locked viewport tag. It scores each screen and gives you one overall score.
Is it free, and do I have to sign up?
It is free and there is no signup. You paste a URL, you get the report on the page, and we never ask for or send an email. The checker stores no IP address and no record of what you scan. Site-wide analytics are covered in our privacy policy.
Which screen sizes does it check?
Four: the outer screen in Safari with its side rail (382 x 580 pt), the outer screen at its full 466 x 678 pt width, the inner screen held wide (951 x 589 pt) and the inner screen rotated tall (669 x 871 pt). These are the sizes Safari gives a page, with the toolbar showing and one tab open, measured on 20 October 2026.
Are those sizes confirmed on a real iPhone Duo?
Not yet. We measured them in Apple’s iOS 27.1 simulator, because the phone goes on sale on 23 October 2026. We will re-check every number on hardware and update the checker if anything moves. Safari’s side rail and toolbar can change a page’s size with tab count and settings, so treat the sizes as the common case rather than the only one.
Does it run on a real iPhone?
No. It loads your page in WebKit, the engine Safari is built on, set to the Duo’s page sizes, screen density and an iPhone Safari identity. That catches layout problems reliably. A small number of iOS-only behaviours can still differ, which is why every result is a starting point and a person should still look.
How is the score worked out?
Each screen starts at 100. Every critical finding takes 15 points, every warning takes 5, and no single check can take more than 30. The overall score is your worst screen, because a page that breaks on one Duo screen is not ready. A screen passes when it loaded and has no critical finding.
What does it not check?
It does not yet test the moment you fold or unfold the phone, Split View (we could not measure it in the simulator), pages behind a login, or what happens as you scroll. It checks the first load of one public page, so check your key pages one at a time.
What if my site fails to load in the checker?
Check that the address works in a normal browser, that the site is public and that it answers on the standard web ports (80 and 443). Sites that block automated visitors or sit behind a login cannot be checked. Try again if the checker says it is busy.
How does this relate to FullBleed?
FullBleed is our Safari extension that lets pages use the whole 466 pt outer screen instead of stopping at the side rail. FoldReady checks your site at both the 382 pt and the 466 pt outer widths, so you can see how a page behaves with and without it.
Building for the Duo
We build and ship for the iPhone Duo.
FoldReady and its sibling FullBleed, the Safari extension that gives pages the full outer screen, are Champlin Enterprises products. If the list is longer than your week, we can help.