Get an extension "Disable HTML5 Autoplay"
You can also run a "noscript" type extension. This is many times safer but more annoying for people that don't wan't to be bothered getting their web browsing setup just right.
Essentially every script on the websites you visit is disabled and you have to go through one by one to activate the ones you want and ignore what you don't.
Upside is no ads, many less cookies and other tracking issues and you can keep videos from loading automatically. You simply click the video box and it will ask to allow the scrip this one time and it will play if you confirm. It is the safest way to browse the net.
Downside is if you don't setup certain scripts stuff like text input boxes or buttons / menus on screen like "post message" won't work.