I already did tests with Furaffinity's image resolution, and now I know what is the maximum free resolution available to draw. The page recommends a resolution of 1440 x 2k, which is a lie, it is possible to have different resolutions than that. A perfectly square 3k image, It is compressed at maximum is 1920 x 1920. A recommended standard rectangular image is 1554 x 2372, and not one more pixel, because the image is compressed to be smaller than its original size. For my part, I recommend publishing your art in high resolution, to Deviantart, but if you want to upload more adult content, I recommend Twitter and Inkbunny. I hope this post has helped you.
https://twitter.com/dachgum/status/.....62061728731136