If you want to download facebook videos and watch them later offline then Snaptube is a easy and fast way to do it. Here is how you can use it:

  1. First open the snaptube app on your phone
  2. Then go to facebook and find the video you want
  3. Copy the video link and paste it in the snaptube search bar
  4. Snaptube will find the video and show download options
  5. Choose the format like mp4 or mp3 and click download
  6. The video will be saved in your gallery to watch anytime

This works for public videos on facebook. For private videos it may not work unless you are loged in. Its free and super simple to use.