Because the apps were built using iOS 27.1 SDK or later, these apps will fill out both the 7.6-inch internal display and the 5.4-inch external screen without using letterboxing or black bars to fill out unused space.
It's been wonderful to see how quickly developers have embraced iPhone Duo, and we're grateful for their creativity and innovation. Today there are well over 100,000 apps built for iPhone Duo already live on the App Store, and thousands of optimized apps are being added to the store each day. In the last month alone, thousands of developers have joined us for workshops in 19 cities around the world to experience iPhone Duo firsthand and bring updated apps to their users. The enthusiasm has been incredible, and we're excited to see the pace of updates continue to accelerate as more and more apps optimize for iPhone Duo.
Susan Prescott, Apple's Vice President of Worldwide Developer Relations
Toolbars and tab bars appear vertically below the status bar. As a result, users have an optimal and consistent experience with these apps as they switch between displays. On Friday, Apple said that it has been adding thousands of apps optimized for the iPhone Duo every day.
These are some of the apps that are fully optimized for the iPhone Duo
To help get enough optimized apps for its foldable iPhone, Apple has hosted more than 50 in-person workshops around the world that have been attended by more than 2,000 developers. Among the apps fully optimized for the iPhone Duo are some first-party Apple apps and third-party titles such as:
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Apple Music
Apple TV
Calendar
Notes & Bear
Files
Netflix
Prime Video
Paramount+
MLB
PGA Tour
Zoom
Slack
Microsoft Word
Instagram
OpenTable
Yelp
To make sure that an app is fully optimized for the iPhone Duo, open the App Store and look for the "Made for iPhone" badge on the app's product page. You can also peruse the What's New section looking for a mention of iPhone Duo support.
Developers have been optimizing apps for the iPhone Duo using iOS 27.1 SDK. | Image by Apple
Also, in the App Store, on an app's product page, make sure to check out the published screenshots to see what the app will look like on the Duo. Speaking of the App Store, Apple still lists "Great Apps on iPhone Duo" (New experiences enter the fold, quips Apple).
The App Store lists the most popular iPhone Duo apps
The App Store also lists the "Most Popular Apps on iPhone Duo." That list is led by the Overcast Podcast App, the Darkroom Photo & Video Editor, Slack, Procreate Pocket, American Airlines, Sky Guide, Google Gemini, Webex, United Airlines, and Zillow. These are the 10 most popular apps for the Duo. Other popular apps include:
Instagram (#11)
ChatGPT (#13)
Lyft (#16)
Threads (#17)
Facebook (#21)
YouTube (#27)
Obviously, Duo users prefer to see all of the apps available for them to install be optimized. Otherwise, when they open an unoptimized app, they see a small window in the center of the internal display flanked by large black bars. This letterboxing allows unoptimized apps to appear in the size they were originally designed for. In iOS 27.1 SDK and later, the apps are resized to fill the internal display.
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Alan, an ardent smartphone enthusiast and a veteran writer at PhoneArena since 2009, has witnessed and chronicled the transformative years of mobile technology. Owning iconic phones from the original iPhone to the iPhone 15 Pro Max, he has seen smartphones evolve into a global phenomenon. Beyond smartphones, Alan has covered the emergence of tablets, smartwatches, and smart speakers.
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