GIF89a

GIF89a is the second major revision of the Graphics Interchange Format (GIF). Released by CompuServe in 1989 as an update to GIF87a, GIF89a added features for animation, transparency, and metadata while preserving backward compatibility with GIF87a files.

Key changes introduced by GIF89a include the Graphics Control Extension (GCE), which enables per-frame delay times and a transparent color index; the Netscape Application Extension for looping animations; as well as the Comment Extension and the Plain Text Extension for metadata. The format continues to use LZW compression for color-indexed images with up to 256 colors in a palette.

Animation and compatibility: GIF89a frames can reuse a global color table or specify local color tables. Decoders that do not support the extensions will typically ignore them and render the first frame. The format became widely used on the Web for simple animated graphics, complementing the still-image use of GIFs.

Legacy: The GIF format’s LZW compression was patented in the United States, which led to licensing considerations during the 1990s. The patents have since expired in many jurisdictions, and GIF remains in use for small, widely compatible images, though newer formats have supplanted it for many applications.