4K movies playback

Anyone know why does my tv display adjust to YUV 444 when movies only use 420 according to inner details of the file (checked using a windows program) and is it alterating the original colour subsampling ?

It adjusts to the highest possible setting at a certain resolution.
Normally it’s 444 up to 4K@30Hz and 420 at higher refresh rates.

Ah ok I prefer to watch films in 24hz as they are filmed at 24fps, alot smoother. I’ll see if it runs/looks ok at 60hz but with 420.

Why would you want to play them at 60Hz?
There’s no problem with displaying 420 chroma video on top of a 444 signal…

I dont but as you said only way to display 420 is a higher hz. Thats what I was gettin at is there a difference with a 420 chroma video but with a 444 display.

4:2:0 content has a quarter of the color information that 4:4:4 can hold. So there is no potential loss in quality, and playing 4:2:0 content in 4:4:4 works perfectly fine.