I've seen them work on my iPhone, but whatever algorithm they're using is horrible. For every frame of animation it seems to want to read from the "start" of t

I've seen them work on my iPhone, but whatever algorithm they're using is horrible. For every frame of animation it seems to want to read from the "start" of the file. For a few frames, it's fine, but anything longer than 2-3 seconds of animation makes it slow to a crawl. Animated gifs are so uncommon anyway (the use cases I've seen where it falls down are lolcat-worthy animations) that it's probably not worth fixing. The 90s-era gif animations probably look good enough.