Yesterday the 20 year Unisys patent for the LZW (Lempel Ziv Welch) compression algorithm expired in the US. This patent is the basis of the popular GIF (Graphics Interchange Format) which is used on many images in web pages. The counterpart Canadian patent expires July 7, 2004, the counterpart patents in the United Kingdom, France, Germany and Italy expire June 18, 2004, and the Japanese counterpart patents expire June 20, 2004.