Fortnite now runs in 4K resolution on the Xbox One X, though the PS4 Pro misses out on its newly introduced enhanced graphics mode.
In today's Fortnite patch 2.50, full 4K resolution has been introduced to the Xbox One X. Meanwhile, the PS4 Pro has received... not much, really. Epic has deployed the dynamic resolution and high quality temporal upsampling that is also available on the standard PS4 and Xbox One, but the Pro has unfortunately been left out.
With the Xbox One X being the only "true 4K" console, meaning that it is able to display in a native 4K resolution with greater frequency as a result of its better hardware, games tend to naturally look better on the Xbox One X than they do on the PS4 Pro. However, with Fortnite Battle Royale being one of the most popular games out there right now, it'll still be disappointing for PS4 Pro owners that they're not able to get a 4K resolution out of the game.
Fortnite Battle Royale isn't exactly the most graphically intensive game, so PS4 Pro owners will hopefully be able to run it in the resolution sooner rather than later. It's not known for its blistering visuals (aside from the good-looking first-person mode concept knocked together by a fan), so even in 4K Xbox One X owners aren't exactly getting the most beautiful game out there, though those Victory Royales will certainly be sweeter with the extra pixels.