So here is the easiest way to disabling videos from autoplaying on Facebook. Install the plugin called F.B. Purity. Once it is installed, surf on over to Facebook. It will pop up a window that will let you customize F.B. Purity. Click on Video Stories on the right. Check the box next to “Disable Autoplay”. Then just save and exit. You’re done.
For chrome users, see my older post: