A photo was posted on my Instagram account, and for about a week, it looked clear and it’s quality was high. However, it suddenly became pixelated to the point of being unrecognizable. I was under the impression that online images do not change, so I would like to ask what caused this sudden change. A similar problem has been evident with Facebook. I downloaded a photo a few months ago from a Facebook page, and it’s size was 459 kB. When I dowloaded it again this morning, onto the same device, the photo was 451 kB large. What causes online photos to deteriorate over time? Is there any way to prevent that?