If you really do tap on an image on the mobile app version of X and hold down your finger, you can save an image in 4K. Pretty cool! No one really knew about it. And per Know Your Meme ...
It has spread widely and “load in 4K” has since become a meme. Users are sharing images on X with “Load in 4K” in the caption, urging others to open the images in the Ultra High Definition ...