It is difficult to describe the JPG quality losses, except by seeing an example image (next page). JPG does not discard pixels. Instead it changes the color detail of some pixels in an abstract mathematical way. JPG is mathematically complex and requires considerable CPU processing power to decompress an image. JPG also allows several parameters, and programs don't all use the same JPG rules. Programs vary, some programs take shortcuts to load JPG faster but with less quality (browsers for example), and other programs load JPG slower with better quality. Final image quality can depend on the image details, on the degree of compression, on the method used by the compressing JPG program, and on the method used by the viewing JPG program.