Blog · 21 October 2026 · 3 min read
Kindle on iPhone Duo: why it looks small, and what you can do
The Kindle app runs in an iPhone-sized window on the iPhone Duo's inner display. Why that happens, what still works, and how to read on the full screen in the meantime.
If you open the Kindle app on an iPhone Duo and unfold the phone, the book does not fill the 7.6-inch screen. It sits in a window the size of an ordinary iPhone, with empty space around it. Nothing is wrong with your phone or your account. The app simply has not been updated for the Duo yet.
This page was written on 21 October 2026, two days before the iPhone Duo goes on sale. We will update it when Amazon ships a new version.
We make Glosa, a reader for iPhone, iPad and iPhone Duo, which comes up at the end. It is not on the App Store yet, and it cannot open books bought from Amazon.
Why the Kindle app is letterboxed
Apple's developer talk on the iPhone Duo explains how the inner display treats each app. An app built with the iOS 26 tools or older keeps its usual iPhone size there, centred on the screen. Only apps rebuilt with newer tools stretch out, and only those built with the iOS 27.1 tools reach all the edges.
The latest Kindle for iOS when we checked was version 7.69, released on 9 October with the note "Several Bug fixes and improvements". It runs in the small window on the Duo, and CNN's review of the phone lists Kindle among the apps that have not caught up yet.
What still works
Everything you use on a phone keeps working: your library, Whispersync of your place, highlights and notes, and the dictionary. On the 5.4-inch outer display Kindle looks as it does on any iPhone, because that screen is iPhone-sized. Only the open inner display is affected. The Duo's new Split View puts two apps side by side, so you may be able to keep Kindle on one side and notes or a dictionary on the other.
What you can do now
The first option is to wait. Amazon updates the Kindle app often, and a version for the Duo may follow. When it arrives, the "What's New" text on the App Store should mention the iPhone Duo or the larger screen.
You can also read Kindle books on the web. Kindle Cloud Reader opens in Safari, which is updated with iOS and fills the inner display. It needs a connection the first time you open a book.
Or read your DRM-free books in an app that fills the screen. Books from Amazon's store carry DRM and only open in Amazon's apps. Your other books are different: free classics, files from publishers and stores that sell without DRM, and your own MOBI or AZW3 files that never had DRM. Those can go into any reader that is ready for the Duo. Our guide to opening MOBI and AZW3 files on iPhone shows how to tell the difference and move them across.
Readers that use the whole screen
Apple Books comes with the phone, so it fits the inner display from day one, and CNN's review says it shows facing pages when the phone is partly folded. Most third-party readers have not said yet what they do on the Duo; we keep a list in The best ebook reader apps for iPhone Duo.
Glosa, our reader, is built with the iOS 27.1 tools and reaches the edges of the inner display. A paged EPUB is set as two pages, one each side of the fold, whether the phone lies flat or half folded. It opens DRM-free MOBI and AZW3 as well as EPUB and PDF, and a double-tap on any word gives its meaning in that sentence, in any of sixteen languages. It is free, and not on the App Store yet. For more options while you wait for Kindle, see Kindle app alternatives for iPhone and iPad.