GFY

GFY is not actually a distinct file format, but it is an MP4 or WebM video that is presented via a HTML 5 video element with options set so as to make it work similarly to an animated GIF (i.e. endless loop with no video controls visible). This is created by Gfycat when a user uploads an animated GIF. This is not really a format to store and preserve animated graphics yourself, but one for a website to present them.

Sample files

 * Sample GFY at GfyCat (This is the original GIF version)