Facebook has announced to make its video autoplay. This feature is great for those who love watching videos. But it's very annoying for those who has limited data packs or not interested to watch online videos. Here you will know about how to disable Facebooks autoplay video:

For Android devices
1. Login into your Facebook account
2. Tap the three-lined button in the upper right corner of the screen.
3. Scroll down and tap 'App Settings'
4. Go to 'Videos in News Feed Start with Sound', tap the toggle to off

For iOS devices
1. Login into your Facebook account
2. Tap the three-lined button at the bottom right corner of the screen.
3. Go to Settings > Account Settings > Sounds
4. Go to 'Videos in News Feed Start with Sound', now tap the toggle to off

Hope this helps