digital file format devised in 1987 by the Internet service provider CompuServe as a means of reducing the size of images and short animations. Because GIF is a lossless data compression format, meaning that no information is lost in the compression, it quickly became a popular format for transmitting and storing graphic files.

At the time of its creation, GIF's support of 256 different colours was considered vast, as many computer monitors had the same limit (in 8-bit systems, or 2⁸ colours). The method used to keep file size to a minimum is a compression algorithm commonly referred to as LZW, named after its inventors, Abraham Lempel and Jacob Ziv of Israel and Terry Welch of the United States. LZW was the source of a controversy started by the American Unisys Corporation in 1994, when it was revealed that they owned a patent for LZW and were belatedly seeking royalties from several users. Although the relevant patents expired by 2004, the controversy resulted in the creation of the portable network graphics (PNG) format, an alternative to GIF that offered a wider array of colours and different compression methods. JPEG (joint photographic experts group), a digital file format that supports millions of different colour options, is often used to transmit better-quality images, such as digital photographs, at the cost of greater size. Despite the competition, GIF remains popular.