GIF

The Graphics Interchange Format (GIF; /ɡɪf/ GHIF or /dʒɪf/ JIF, ) is a bitmap image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite and released on June 15, 1987.

The format can contain up to 8 bits per pixel, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It can also represent multiple images in a file, which can be used for animations, and allows a separate palette of up to 256 colors for each frame. These palette limitations make GIF less suitable for reproducing color photographs and other images with color gradients but well-suited for simpler images such as graphics or logos with solid areas of color.

GIF images are compressed using the Lempel–Ziv–Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality. While once in widespread usage on the World Wide Web because of its wide implementation and portability between applications and operating systems, usage of the format has declined for space and quality reasons, often being replaced with newer formats such as PNG for static images and MP4 for videos. In this context, short video clips are sometimes termed "GIFs" despite having no relation to the original file format.

CompuServe introduced GIF on 15 June 1987 to provide a color image format for their file downloading areas. This replaced their earlier run-length encoding format, which was black and white only. GIF became popular because it used Lempel–Ziv–Welch data compression. Since this was more efficient than the run-length encoding used by PCX and MacPaint, fairly large images could be downloaded reasonably quickly even with slow modems.

The original version of GIF was called 87a. This version already supported multiple images in a stream.

In 1989, CompuServe released an enhanced version, called 89a, This version added:

The two versions can be distinguished by looking at the first six bytes of the file (the "magic number" or signature), which, when interpreted as ASCII, read "GIF87a" or "GIF89a", respectively.

CompuServe encouraged the adoption of GIF by providing downloadable conversion utilities for many computers. By December 1987, for example, an Apple IIGS user could view pictures created on an Atari ST or Commodore 64. GIF was one of the first two image formats commonly used on Web sites, the other being the black-and-white XBM.