After years of waiting, Twitter users who are animated GIFs lovers can now be relieved that their animation is viewable directly on Twitter.com, and Twitter for Android and iOS. You’ll no longer need to open a new window or launch another app to watch animated GIFs play.
One caveat is that this is not a ‘direct’ support for GIF format. Instead, Twitter is converting your GIF file into mp4 movie when you upload them. And you need to make use of Twitter’s pic.twitter.com image upload service in order for this work.