In a recent Facebook iOS update, the app gained the ability to automatically play muted videos from your News Feed. While this can be slightly amusing for the first fifteen minutes of use, it can get annoying over time. Not to mention it can use ungodly amounts of cellular data if you use Facebook frequently. Thankfully for the sake of your sanity and phone bill, you can disable the feature for when your iPhone is using cellular data. Unfortunately, at this time there is no way to disable the feature over Wi-Fi, but hopefully we’ll see the addition of this in a future update.
To disable auto play, launch the Settings app and scroll down until you find the option for Facebook. Tap on this option and then tap on the button labeled Settings. Within this window is an option labeled Auto-play on WiFi only, enable this option. To ensure that the changes are put into affect, quit the Facebook app and reopen it.
Via: OS X Daily