An animated GIF is a GIF file that includes multiple images or "frames." These frames are played back in sequence when the file is opened or displayed in a web browser. The result is an animated clip or a short movie.
The GIF file format includes a Graphics Control Extension (or "GCE block"), which enables a single GIF file to store multiple frames. This section also specifies the delay between frames, which can be used to set the frame rate or insert pauses at certain points within the animation. Another section, called the Netscape Application Block (NAB), specifies how many times the animation will repeat (a setting of "0" is used for infinite repetitions).
In the early years of the Web, animated GIFs were a popular way to display motion and liven up websites. They were commonly used for advertisements, such as banners and leaderboards. As Flash animations became more popular, animated GIFs became less prominent. However, animated GIFs have recently seen a resurgence on the web since they are supported by all platforms. For example, Apple's iOS does not support Flash animations, but can display animated GIFs.
Several image editing programs, such as Adobe Photoshop and GIMP, can be used to create animated GIFs. Other graphics programs can merge multiple image files into a single GIF. Some video utilities can even convert short videos to animated GIFs. While this can be useful for sharing small videos on the web, the GIF format is not as efficient as the MPEG format for storing videos longer than a few seconds.