Apple clears up 120Hz iPhone 13 Pro confusion for developers

Apple has also promised a bug fix for some Core Animation problems.

What you need to know

Apple has cleared up some confusion about 120Hz on iPhone 13 Pro.
The company says developers can take advantage of the feature but they have to opt their app in.
The company says this is to maintain optimum battery life.

Apple has confirmed that developers can in fact use 120Hz on the iPhone 13 Pro and Pro Max, but that they have to opt their apps in to using the feature.

On Friday, some developers noticed that not all apps were taking advantage of the iPhone 13 Pro’s 120Hz refresh rate. The feature would work for scrolling or full-screen transitions, but that all other animations in third-party apps were capped at 60Hz.

Am I correct in seeing that UIView.animateWithDuration APIs aren’t clocked at 120Hz on iPhone 13? On UIScrollView, system ones, and Metal by the looks of it, rest is still 60Hz? pic.twitter.com/t3MeM9cj0E

— Christian Selig (@ChristianSelig) September 24, 2021

There was a pretty tricky workaround, but Apple has now confirmed that apps can in fact take advantage of this feature by adding a new plist entry to their app, declaring it uses the higher frame rate.

Apple has issued new documentation explaining ProMotion refresh rates for the iPhone 13 Pro to developers which states:

On iPhone 13 Pro or iPhone 13 Pro Max, add the following key to your Info.plist file to enable the full range of refresh rates for CADisplayLink callbacks and CAAnimation animations in your app:

CADisableMinimumFrameDurationOnPhone

Your app must use this key to access higher frame rates (above 60Hz) it sets in the preferredFrameRateRange hint API. The iPad Pro doesn’t require this special configuration.

The new 120Hz display in the iPhone 13 Pro is one of the biggest new features in Apple’s best iPhone this year, offering smoother scrolling, viewing, and usage. It also has a variable refresh rate for battery preservation and a new Super Retina XDR display which is much brighter than the old one.

Apple has also reportedly confirmed that there is a bug affecting some animations using Core Animation and that a fix in iOS 15 is on the way.