the easiest way to download facebook video. u don't need to install any software,plugins or add-ons.
if you are using android supportable devices on mobile site then open facebook on chrome for android.open video of your friends or pages. then play video first and click on the "option" botton of your mobile,save video. that's set... but for those peoples who uses desktop site how do you do.. ?
if you are using desktop site then change the link desktop to mobile from the link you see at top of the window. just like this picture ..
if you are using desk top site then click on the video.then change the link from desktop to mobile site just like shown in the above picture. remove "www" and type "m". link should be like this >> http://m.facebook.com.... remove 'www" the put 'm' then hit enter.
then right click once and save video. its easy and u can do it on all of your browser..