If you've also noticed Unreal Engine games being blurry in borderless mode unless your monitor uses a DPI scale of 100%, then make sure to change the "bAllowHighDPIInGameMode" config!
I made a PR for it:
github.com/EpicGames/UnrealE…
Games absolutely need to render at a 1:1 pixel ratio, with no spatial scaling from the OS increasing lag and blurriness.
Especially when many games don't even show the borderless mode resolution, so gamers aren't informed of the limitation. If they are lucky enough to notice, they are forced to use Fullscreen Exclusive mode, which is really not nice in 2026!
Hopefully Epic merges this.
I don't see what good the current default does 😀.
@UnrealEngine