https://wccftech.com/fortnite-xbox-one-x-update-released/

Epic Games has released the Fortnite Xbox One X update which boosts the game’s visual settings comparable a PC on “Epic” quality.

The update offers 4K resolution support on Xbox One X, although the content isn’t rendered in native 4K. Instead, content is being rendered in 80% of 4K and then upscaled to 4K using a high-quality software upsampler. Fortnite’s Xbox One X HUD is being rendered in 4K however.