With a few exceptions, most mobile games aren't exactly known for running at the highest frame rates. Some devices, like Asus' ROG Phone and Razer's Razer Phone, try to improve the situation, but many titles are locked at 30 FPS regardless of the hardware you're running them on.
This can be a particularly-frustrating restriction for gamers who tend to play more competitive titles like Fortnite. Though it's not as action-packed as, say, Call of Duty, the best Fortnite players still need to have lightning-fast reaction times to survive during shoot-outs.
As many of those players will likely tell you, running the game at a higher frame rate can be a direct competitive advantage, primarily because it allows your in-game movements to more accurately mirror your real-time inputs.
To that end, there's good and bad news for Fortnite's mobile users today.
We'll start with the good stuff: Epic Games has officially implemented a 60 FPS option into the game, which should give players a much smoother experience. The downside is that, for now, the option is only available on a few devices; Apple's iPhone XS, XS Max, and XR, specifically.
This means that Android users (and iOS users who haven't upgraded to Apple's latest phones) are out of luck for the time being. However, Epic Games has said in a statement to The Verge that it's working on optimizations that will allow it to bring the "60hz mode" to Android devices in the future.