iOS 15.4 will let apps make proper use of iPhone 13 Pro's 120Hz ProMotion display

Source: Apple

What you need to know

Apple's iOS 15.4 update is now in the hands of developers.
A bug that locked apps to a 60Hz refresh even on iPhone 13 Pro and iPhone 13 Pro has been fixed.
Third-party apps will be able to take full advantage of 120Hz ProMotion on high-end iPhones once iOS 15.4 ships to the public.

Apple's new iOS 15.4 update will allow third-party apps to make full use of the 120Hz ProMotion display in iPhone 13 Pro and iPhone 13 Pro Max.

When Apple released iPhone 13 Pro and its larger sibling late last year, the addition of a super-fluid ProMotion feature was a big deal. 120Hz refresh should have made apps buttery smooth during movement and scrolling, but a bug was discovered that prevented some apps from anything higher than 60Hz. According to Apollo developer Christian Selig, that now appears to have been dealt with. Apple confirmed to them that the bug has been fixed in iOS 15.4 and that "all apps automatically get 120Hz animations" with the update installed.

This is indeed good news and it is something that has been confirmed by Selig's own tests.

Source: Apple

Some rumors have suggested that the upcoming iPhone 14 lineup will offer 120Hz ProMotion across all devices, although that seems unlikely given the costs and production requirements involved. For now, anyone with an iPhone 13 Pro or iPhone 13 Pro Max can look forward to iOS 15.4 arriving and then enjoying some silky smooth in-app animations.

Unfortunately, we don't yet know when we can expect iOS 15.4 to be released to the public — Apple only made the first beta available to developers yesterday.