Shopping v26.10.6
Does Costco work on iPhone Duo?
It works, but with black bars. Costco 26.10.6 is built with the iOS 26.2 SDK, so iPhone Duo runs it in a phone-sized window on the inner display.
At a glance
- Inner display (7.6″)
- Black bars
- Outer display (5.4″)
- Works normally
- Built with
- iOS 26.2 SDK
- Version 26.10.6, read Nov 1, 2026
- iPad version
- Yes
- Layout already handles big screens
- Latest version
- v26.10.6
- Oct 30, 2026
- Duo in release notes
- Not yet
About Costco
Costco is made by Costco Wholesale Corporation and first came out on the App Store in July 2012. It's #81 on today's US App Store top charts. It has 1,317,948 ratings on the US App Store, averaging 4.9 stars. Version 26.10.6 came out on Oct 30, 2026 and needs iOS 16.0 or later. It's free to download. Among the 28 shopping apps we track on the US App Store, 11 already fill the inner display, 2 are partly adapted and 15 still show black bars. By number of ratings, Costco is #16 of them.
From its App Store listing:
It's easy to save time and money while on the go, with the Costco Mobile App! We've improved our mobile app, to make it easier for members to access the incredible values found only at Costco. DIGITAL MEMBERSHIP CARD: Access your membership card from the home page of the app. Use your membership card to enter the warehouse and at checkout. SHOP: Browse Costco.com’s unique and expanded selection, w…
On the inner display
Apps built with older SDKs are placed in a phone-sized safe area on a black background. Everything works; you just don't get the bigger screen.
In Split View
iPhone Duo is the first iPhone that can show two apps side by side, and every app takes part — including Costco. 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 26.10.6 is built with the iOS 26.2 SDK
Apple runs apps built with the iOS 26 SDK or earlier in a phone-sized window on the inner display.
- : Not confirmed yet → Black bars — built with the iOS 26.2 SDK
Latest release notes
Version 26.10.6 · Oct 30, 2026
Bug fixes and improvements.
Questions
Does Costco work on iPhone Duo?
It works, but with black bars. Costco 26.10.6 is built with the iOS 26.2 SDK, so iPhone Duo runs it in a phone-sized window on the inner display.
Does Costco 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 Costco 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.
Why does Costco have black bars on iPhone Duo?
Apps built with the iOS 26 SDK or earlier run in a phone-sized window on the inner display, and iOS 27 builds can still leave some space empty. The bars disappear once the developer rebuilds the app with the iOS 27.1 SDK — you only need to update the app.
When will Costco fill iPhone Duo's inner display?
When its developer releases an update built with the iOS 27.1 SDK or later. We read the SDK of every new version of Costco within about a day of its release and update this page.
What can I do about the black bars until then?
Use Costco on the outer display, where it works like on any iPhone, or put it in Split View next to another app on the inner display so less of the screen goes unused.