The term "wallpaper" was used in Microsoft Windows before Windows Vista (where it is called the "desktop background"), while macOS refers to it as "desktop picture". On older systems which allowed small repeated patterns to be set as background images, the term desktop pattern was used.
Wallpaper images are usually copyrighted as many other digital images found on the Internet, and as such, most websites collecting and sharing wallpapers, as well as the users downloading from them are an example of mass copyright infringement, a phenomenon which challenges the meaning plus illegality of digital piracy and the validity of current copyright legislation around the world.
