Right-click the Fortnite executable file ( FortniteClient-Win64-Shipping.exe ), go to Properties > Compatibility, and check Disable fullscreen optimizations .
Click the three dots on Fortnite in your library, select Options , and uncheck High Resolution Textures to save disk space and improve loading times. *INSANE* Fortnite Chapter 3 Season 3 FPS Guide!
Cap this at your monitor's refresh rate (e.g., 144Hz or 240Hz) to ensure smooth frame timing. go to Properties > Compatibility