this is a new format that supports lossless and loss compression quality for images on the Internet. The Google Company developed this format specifically to do work online as quickly and conveniently as possible. The main advantage is that its file size is small compared to other image formats, but similar in image quality.
This format is used to store background images in uncompressed form in the X Windows System user interface for remote server maintenance. It stores a 'dump' or screenshot of the window or background of the client program. It may include different colors depending on the capabilities of the graphics card that is used to create the XWD file.