There are times when some of your facebook friend has posted a video which you like very much and watched many times, you may want to download this video on your computer and store it on your hard drive. You can download any facebook video if you have firefox or google chrome installed on your computer, by following the procedure below.
1. Make sure you have firefox installed, or you can download from here
2. You will first need to install the greasemonkey addon from here
3. Once you have installed the greasemonkey extension, you will need to install the facebook video download userscript from here
After following all the above steps, just refresh or load the facebook page containing the video and you will see a small link below the facebook video which allows you to download it as shown in the image below.
In order to download the video just right click on the link Download Video and then select Save target as
to save the video on your computer.
For Google Chrome
The download procedure remains the same in google chrome too, however in order to start downloading you can directly install this user script from here
Note: This userscript is for the Facebook Video application, which allows users to share personal videos with their friends. Facebook has stated in its Video FAQ that "Users will not be able to export or download videos from Facebook." This is the first userscript to support downloading Facebook Videos and it adds features that Facebook refuses to implement.
this script will work for all the facebook videos only, not for those videos which are on youtube, for downloading youtube videos you can check out here