How to turn off the auto-play setting for Video on Facebook on IPhone.
Step 1: Log in your account and click on the symbol in the lower right corner of the screen.
Step 2: Scroll down and then choose “Settings”.
Step 3: Click on “Account Settings”.
Step 4: Choose “Videos and Photos”.
Step 5: Choose “Autoplay”.
Step 6: Select “Never Autoplay Videos” to complete.
These above steps are to stop auto-play settings for video on ios devices.