Twitter is trying out a dedicated GIF button that lets you pick from a set of already made images in order to add animation to your post. A number of users have said they see the GIF button, but the feature is not available to everyone yet. For those who have it, the button is located between the image and poll options.
Once you click the GIF button, you are presented with a set of trending images and images from a variety of mood categories.
Twitter has not said where the GIFs are coming from or when the feature will roll out to everyone.