On the computer, you need to download facebook private videos by using page source codes. But in the f2mate android app, you can easily download Facebook private video by pasting URL. But for this, you have to log in with your Facebook account on the f2mate Facebook video downloader app. F2mate browser section will help you to download private video on your smartphone.
At first, You need to copy facebook video URL. If you don't know, Read how to copy video URL on Facebook app?
Now you need to download the f2mate Facebook video downloader app from Google Play Store. After that, open the f2mate app on your smartphone. You will see a short tutorial to use this app. Then you will be on the main Facebook video downloader page. But, to download Facebook private video, you need to go browser section of f2mate app then paste your link to the browser URL box and hit go. See the following image to know clearly.
After opening Facebook you need to login here with your Facebook account. Don't worry! f2mate is 100% safe browser like another. If you already login with your Facebook account, then you will directly go to the video page. You have login exact that account from that you copied video URL. After login, you will go to your video page.
Then download the video simply as usual.