Welcome to Duo Tracker

When a foldable unfolds, the screen ratio changes. Plenty of apps are simply scaled up rather than designed for it: columns squeeze together, whitespace suddenly balloons, and the transition between the folded and unfolded states breaks. These problems rarely make it into release notes; they end up scattered across forum screenshots and personal testing, which makes the simple question — can I use this app right now? — surprisingly hard to answer.

Duo Tracker exists for that question: a directory that records iPhone Duo compatibility per app version.

What the site does

It answers one thing — can this app be used properly on the unfolded screen, today?

The answer is not "a new version shipped, so probably". It is tied to:

• a store region (Mainland China / United States)
• a specific app version and iOS version
• the screens and actions that were actually checked

Every result is bound to a version, and a new release does not inherit an old result. When evidence is insufficient, the status stays not checked instead of being guessed.

When it helps

• Before switching to a Duo, to see whether the apps you use every day keep up;
• After setting up the device, when an app looks odd unfolded and you want to know whether it is you or the app;
• When an app ships an update and you want to know whether the earlier result still holds;
• When you are looking for apps genuinely designed for the larger canvas rather than stretched to fill it.

What you get

• A checkable compatibility status: adapted, partially adapted, in progress, not adapted and not checked — five states, each with its own definition.
• A direct line to the store: every app links to the App Store of the matching region.
• Records split by region: Mainland China and the US are separate datasets; your account region can change what you see and download.
• A restrained recommended list: 32 apps for now, drawn from hands-on use and visitor feedback.

What is in the directory today

As of October 23, 2026, the site tracks 4,670 distinct apps across 4,985 regional records:

	Mainland China	United States
App records	2,439	2,546
Adapted	93	82
Partially adapted	3	1
In progress	8	7
Not checked	2,335	2,456

A few notes on how those numbers are counted:

• Coverage is the top 200 free apps in Mainland China, the top 100 in the US, plus the top 50 of each of the 26 official Apple categories in both regions, deduplicated by App ID — so one app can have a record in each region.
• "Not checked" does not mean "not compatible"; it means there is not enough evidence yet. It is also the largest group by far.
• Adapted and partially adapted together account for 179 records, each checked by hand.

The sections of the site

App directory / US directory: four entries by interface language and store region, defaulting to Chinese with the China store. Sorted by free chart rank by default, filterable by status and category, and searchable by app name, developer or App ID. Opening an app shows the store version, tested version, OS version and the verification notes.

Recommended: apps the maintainer picked for a complete experience on the Duo. Each one carries a verified official App Store link, and the detail dialog can generate a share card — 3:2 landscape or 3:4 portrait, portrait by default.

Inclusion standard: what each of the five states means, how a conclusion is reached, and why a version change triggers a recheck. Start here if a status looks questionable.

Updates: this page. Newly added apps, tweaks to the site and changes to the inclusion standard, with an RSS feed.

About and Privacy: where the data comes from, how the site relates to Apple, and what it does and does not record about visitors.

What comes next

The directory keeps following the charts, and manual checks are filled in one by one. If you find an app that is missing, or hit a problem that is not recorded here, the feedback form in the footer is the fastest way to tell us — that kind of report is worth more than any automated crawl.