How we test
Disclosure: I make Biombo, an iPhone Duo app. That's a stake in the Duo doing well, and you should know it when you read a verdict here.
Duoworthy has two layers, and every page tells you which one you're reading. The automatic check covers every app we track, every day. The hand test covers a few apps, on my own iPhone Duo, posture by posture.
The automatic check
Every day the site looks each app up on Apple's public App Store data: version, release date, category. It also reads which screenshots the App Store listing carries.
- Made for iPhone Duo The listing has screenshots made for the Duo's cover screen (1398 × 2034) or inner screen (2007 × 2853). That's where Apple's badge comes from, and we show it as Apple's data point.
- Not confirmed No Duo screenshots, but the current version came out after Apple started taking apps built with the iOS 27 SDK. It may fill the Duo's screens or it may not.
- Letterboxed The current version is older than that, so it can't have Duo support yet.
Apple hasn't published the date it started taking iOS 27 SDK builds. Until it does, we use Sep 1, 2026, early on purpose: a date too early only turns some “letterboxed” apps into “not confirmed”. The rules are code, not a language model: the same listing always gets the same answer. Screenshots are checked again when a version changes, and once a week otherwise.
What the automatic check can't tell you is how an app behaves in laptop, book or tent mode. Only a hand test can.
The hand test
- Cover
- Open
- Laptop
- Book
- Tent
I install the app on my iPhone Duo and use it in all five postures: closed on the cover screen, fully open, laptop, book and tent. I record the screen and film the device in each posture, so you can see what I saw.
Each posture gets great, works, poor, or “not for this posture”. The app gets one verdict: Duoworthy, fits, meh, or not there yet. The verdict is mine, signed, with the version and the date. When the app updates, the old test stays in its history.
If a developer gave me anything, a promo code or early access, the test says so. So far no app has been tested by hand.
What we don't do
- We don't copy other directories' verdicts. From them we only take App Store ids, to know which apps exist.
- We don't show App Store star ratings.
- Paid placement, if it ever exists, is labeled “Sponsored”.
The data is open: /data/apps.json, under CC BY 4.0.
Guido Crego