Apple has named more than 50 apps that are or will soon be built for the iPhone Duo, from Netflix and Zoom to Slack and the MLB app, and it's adding a “Made for iPhone Duo” label in the App Store so you can spot them. Apple's list also takes in Fantastical, Flighty, Instagram and DoorDash. Things 3.25 is already out, and it gives Things a sidebar on a phone for the first time. Microsoft's Word and Outlook are still a few weeks away.
Every other iPhone app still runs on the Duo, but one built on the iOS 26 SDK or earlier sits in the middle of the open screen with black bars down both sides. Apps built on iOS 27.1 or later fill both screens, though filling the screen isn't the same as a layout made for the fold. Developers couldn't send Duo apps to Apple until October 8, AppleInsider reported, and outside the companies shown at the launch, few or none had a Duo to test on.