JPG Artifacts

What are "JPG artifacts"?

JPG artifacts, or JPEG artifacts, are distortions in a digital image that appear when you open a JPG file and save it in the JPG format again and again. They appear because JPG is a lossy compression format, which means every time you save an image as JPG, the original data of the pixel colors is lost during the compression process. When you open a JPG file, the data in the file is uncompressed into pixel data, and when you save it, the pixels are recompressed to the JPG format, which causes the loss of some data. Done multiple times, the losses accumulate and the pixels become clearly different from what they originally used to be. This phenomenon is called JPG artifact, or, more generally, as it may occur in other lossy formats such as MPEG video, compression artifacts..