Blurred texts

[fading bough]

you might wanna check your camera, surface, or window sizes as those are some improperly scaled pixels

if you toss a sprite there with no scaling, does it also look the same?

@spiral trail

[fading bough]

1080p scales up to 4k in a perfect 2x, are you drawing to the draw event or draw gui? the gui can have it's own set resolution, maybe check with display_get_gui_size or try display_set_gui_size

this also might help
https://www.youtube.com/watch?v=_g1LQ6aIJFk

when you scale to 4k how are you doing it?

full screen mode? just resizing the window?

[fading bough]

fullscreen might be the game setting the game to full screen mode, and that is not upscaled, so your monitor is handling that and thus making it 'blurry'

as I don't see any blur in your screenshots

I personally dont use the built-in fullscreen mode

I just use boarderless window and set the window to the screen's size