Set your GPU scaling to "Full Screen" to ensure the image stretches to fill your monitor.
Depending on how much "stretch" you want, here are the top picks for 16:9 monitors: Fortnite Stretched Resolution: Best GameUserSet...
the file, right-click it again, and check Read-only so Fortnite doesn't reset your settings. Best Stretched Resolutions for 2026 Set your GPU scaling to "Full Screen" to