xv is a shareware program written by John Bradley to display and modify digital images under the X Window System.
While popular in the early 1990s ("XV is widely considered to be the preeminent image viewer for the X Window System"[2]), no official releases have been made since December 1994.
Bradley was unable to negotiate the LZW patent licence necessary for encoding the then-popular GIF format.
Until at least 2000, Bradley collected third-party updates to xv, for example, support for the PNG image format.
While this concept limits what xv can do compared to some alternatives, the functionality it provides can be applied very conveniently and efficiently.