Go to
SteamLibrary\steamapps\common\ARK\ArkGame\Saved\Config\WindowsClient\GameUserSettings


Then scroll down under [/script/arkgame.arkgameusersettings]

Change Resolution Setting in notepad to this

ResolutionSizeX=3840
ResolutionSizeY=2160

DesiredScreenWidth=3840
DesiredScreenHeight=2160

LastUserConfirmedDesiredScreenWidth=3840
LastUserConfirmedDesiredScreenHeight=2160

After its recommend to set it in properties to Read Only.


I also recommend going to the game ArkGameClient Application and setting Disable fullscreen optimizations on in compatibility settings. As well as setting High DPI scaling Override behavior in Dpi settings to Application.