You can convert most GIF files to webp, which lemmy can use, and those are MUCH more efficient in terms of quality for the space used. But for some reason if you try to upload a GIF to lemmy it turns it into an MP4 file, instead. It’s generally much better to convert to webp first, or better yet create in that format to begin with.

Those are actually not GIF files, they are *.webp files. I’m not sure if GIF format is supported, honestly.