Apple’s first foldable goes on sale today, October 23, and the strangest thing about it isn’t the hinge.
According to YouTuber Marques Brownlee’s review, it’s that many popular apps don’t yet know what to do with a screen this big.
Brownlee's X post already clocked up 10 million views.
The quirk
Brownlee shows "unoptimised" apps behaving as they would on an older iPhone, with buttons in their usual places and a large bar of empty black space down the right side.
He then showed apps that display a black bar on the outer screen and run as tiny iPhone apps on the inner one.
He said Google apps such as Gmail and Maps have not been optimised.
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That matters more on this phone than on rivals. The Duo is so small closed that you have to unfold it for almost everything. So the device built around its big screen often wastes it.
The current state of apps on iPhone Duo: https://t.co/1jJt58zXN8 pic.twitter.com/p2ADO0fbCb
— Marques Brownlee (@MKBHD) October 21, 2026
Which apps
Lists vary by outlet. Dexerto reports Brownlee pointed to Spotify, Google Maps, Discord, X and Google Calendar.
Another summary adds Waze, and says early adopters like Instagram and Carrot Weather have already "updated" or "Duo-optimised:".
Spotify reportedly stretches a bit when unfolded, but most others don’t.
Apple’s own apps are a different story: Apple redesigned them to use the folding displays.
Brownlee calls them a "blueprint" for how a Duo-optimised app should look, adding it may take up to six months to fix the user-interface issue.
The rest of the review
Brownlee’s verdict is that the Duo is polished around the edges but rough in the middle.
He praised the display, hinge, battery life and software animations, and criticized the weight, average camera, missing Face ID and unoptimised apps, calling apps the "biggest downside" right now.
He also noted there’s no telephoto lens, no ProRes or Log video, and a fingerprint sensor with a noticeable delay.
He verdict: most people should skip it, though he calls it fun to use.
The price is $1,999, or $3,199 for 2TB.
The reaction
Mark Gurman of Bloomberg said the reviews are among the most brutal Apple has had in a long time, Vision Pro aside.
Some preorder buyers said the review made them cancel or rethink their orders.
How long will it last?
Estimates differ.
While Brownlee expects most major apps to be adapted in about six months, Gurman believes the problem could be resolved in the coming weeks.
There’s a caveat. Brownlee acknowledged some apps may never get dedicated Duo support.
What it means
For now, the Duo suits someone for whom $2,000 isn’t a big amount and who wants a pocket iPad Mini.
Those mostly using Spotify, Maps, X or Discord, expect black bars and small layouts until developers update.
If you’re buying today, check whether your must-have apps have shipped Duo versions.
Other sources disagree with Brownlee on small details such as which apps are affected and how fast fixes will arrive, so it's best check the app-by-app status before you buy.