[ogurechny]

Even worse, GIF was not intended to be just an “animated image format”, it was “general purpose media streaming format” which incorporated frames/layers, sequence ordering, palette switches, and compression (also, one couldn't be sure that client hardware can decode and paint even a single frame fast enough).

Some old picture book or presentation type GIF files have 0 delay time between frames (doesn't work well with software of later decades, when GIF animations became common), and 0 is “draw as soon as possible” in the specification. Even a simple viewer program without support for metadata or user interaction would have to wait for each frame to be received via modem link, and it would take some time, especially for full screen images. Therefore, a competent GIF viewer software should have an option to simulate 1200 baud download for those old files, and compute the additional delay based on frame size in bytes.