How we know

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  Ready

  Fills the whole inner screen.

  Built with the iOS 27.1 SDK or later.

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  Partly ready

  Fills most of the screen, with a black strip on the right.

  Built with the iOS 27 SDK.

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  Not ready

  Runs in an iPhone-sized window with black bars on both sides.

  Built with the iOS 26 SDK or older.

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  Not confirmed

  We don’t have proof either way yet.

Each frame is the inner screen at its real proportion, with the bars where the iPhone Duo simulator draws them. This comes from Apple’s own guidance for developers: Prepare your app for iPhone Duo.

Release date

An app can’t use an SDK that didn’t exist when it was released. If its latest version came out before the iOS 27 SDK, it’s Not ready, for certain. If it came out before the iOS 27.1 SDK, the best it can be is Partly ready. Apps built into iOS are the exception: they ship inside iOS itself.

Apple’s own apps

Apps built into iOS, like Mail, Safari and Wallet, are Ready: Apple ships them as part of iOS 27.1, the software iPhone Duo runs, whatever date their App Store listing shows. Apple’s other App Store apps are Ready when their latest version came out after the iOS 27.1 SDK, because Apple builds its apps with its latest SDK. Older ones follow the release-date rule above.

Our own check

We open some apps ourselves on our own iPhone Duo and record what the inner screen shows. A look on the device settles that version, and the app’s page says so, with the date.

Featured by Apple

Apps in Apple’s “Great Apps on iPhone Duo” collections on the App Store.

Developer says so

Release notes that say the app supports iPhone Duo. We quote them on the app’s page. This is the developer’s word, so we show it as such.

iPhone Duo owners

Owners tell us how an app looks on the inner screen, with a screenshot as proof. The browser checks the screenshot on the spot and sends us only a small grayscale copy, which we check again; we never store screenshots. Two owners’ matching screenshots settle it, and one screenshot proves one report: the same image can’t be used again for another app, version or person. If owners disagree, we wait for more.

Developers

Developers tell us through their release notes (“Developer says so” above): only they can write them. We don’t take “I made this app” on this site, because we couldn’t check it.

App Store badge

Two owners reporting, with screenshots, a “Made for iPhone Duo” badge on the app’s App Store page, when its release date allows it to be Ready.

Other trackers

Some apps are Ready because another iPhone Duo tracker (FoldHunt, DuoDiscover or iPhoneApplicationList) lists them as ready, and nothing we hold says otherwise. That’s their word, not our proof, so the app’s page names and links the tracker, we keep checking the app every day, and owners can still report: one owner’s screenshot that disagrees outweighs the listing. Our headline count of Ready apps leaves these out.

Earlier versions

Once an app is confirmed Ready, later updates keep it: developers don’t go back to older SDKs. Partly ready and Not ready aren’t carried forward, because the next update can fix them.

“Ready” means the app fills the inner screen with no black bars. It doesn’t mean the app makes good use of the bigger screen: some apps simply stretch their iPhone layout. We report what the App Store, the app’s developer, iPhone Duo owners and other trackers tell us, not how good the experience is.