I don’t know what Twitter does with the gifs but it freezes my old netbook when I try to play them. I can play videos from youtube but I can not play a gif on Twitter!
In case of twitter, there's an important difference in uploading video vs gif. Although a gif is converted to video, it will autoplay and loop without any user control available, just as it was a gif (sadly, you can't download/drag as a gif). If you upload as a video, if will behave like regular video
