No need for Social Fixer... at least not for this. (Score 1)

As others have pointed out, no need for a browser extension to handle this because it's a simple setting. As the developer of Social Fixer, I did post info to users about how to turn this off months ago: https://www.facebook.com/socialfixer/photos/a.382610684341.167165.174424289341/10152145424839342/

Unfortunately, the setting doesn't persist across devices/apps. So setting it on the web won't help mobile anyway. Supposedly auto-play videos were only ever supposed to auto-play if the user was on wi-fi, but I don't think that's actually how it works.

Most of Facebook's decisions and actions are remarkably anti-user. As in, not in the users' best interests, but in the interests of the advertisers, publishers, share holders, and people with the last name Zuckerberg. I often wonder why we all continue to fund this site through content and ad views. It seems like an abusive relationship, but we just won't leave!

[ ps, thanks for the direct link to the Social Fixer site! It won't help with this specific issue, but it will help with many others. :) ]