News v12.40.1
Does X work on iPhone Duo?
Yes. X runs full screen on iPhone Duo's inner display, though it doesn't have Duo-specific features yet.
At a glance
- Inner display (7.6″)
- Full screen
- Outer display (5.4″)
- Works normally
- Built with
- Not read yet
- We read each app's build SDK after it updates
- iPad version
- Yes
- Layout already handles big screens
- Latest version
- v12.40.1
- Nov 4, 2026
- Duo in release notes
- Not yet
About X
X is made by X Corp. and first came out on the App Store in October 2009. It's #21 on today's US App Store top charts. It has 11,167,233 ratings on the US App Store, averaging 4.6 stars. Version 12.40.1 came out on Nov 4, 2026 and needs iOS 15.0 or later. It's free to download. Among the 14 reading apps we track on the US App Store, 8 already fill the inner display, 3 are partly adapted and 3 still show black bars. By number of ratings, X is #1 of them.
From its App Store listing:
X (formerly Twitter) is a social media app where you can follow breaking news, live events, and trending topics as they happen. Sports, tech, music, politics: whatever you're into, the conversation starts here, raw and unfiltered. It's also a place to be heard. Post your take on the day's news, go live, and grow an audience for whatever you create. Millions of people come to X every day to find ou…
On the inner display
The app reaches the edges of the inner display. Text and controls stay a comfortable size instead of being blown up.
In Split View
iPhone Duo is the first iPhone that can show two apps side by side, and every app takes part — including X. Open it on the inner display, then add a second app next to it. You can save the pair and come back to it later.
Duo-specific features
None confirmed yet. Duo-specific features include side toolbars, layouts that react to the fold, and content on the outer display while the app is open inside.
Evidence & history
App build,
Version 12.40 is built with the iOS 27.1 SDK
Apps built with the iOS 27.1 SDK or later can use the whole inner display.
- : Not confirmed yet → Full screen — built with the iOS 27.1 SDK
Latest release notes
Version 12.40.1 · Nov 4, 2026
We made improvements and squashed bugs so X is even better for you.
Questions
Does X work on iPhone Duo?
Yes. X runs full screen on iPhone Duo's inner display, though it doesn't have Duo-specific features yet.
Does X work on the outer display?
Yes. iPhone Duo's 5.4-inch outer display behaves like a regular iPhone screen, so every iPhone app works there as usual.
Can I use X in Split View on iPhone Duo?
Yes. On iPhone Duo every app can be placed side by side with another app on the inner display — developers don't need to opt in. How comfortable it feels at half width depends on the app's layout.