For Android and iOS they (Facebook) allow to restrict this to “Auto-play videos on Wi-Fi only” but even with my MacBook I am rather often only “on the Internet” through a 3G/4G modem, and “my data plan” is just as much concerned as a smartphone or tablet owner’s one. I also want to be able to unallow auto-started videos. It’s not covered by the article referred to above, but it looks like (currently) through “Videos > Video Settings > Auto-Play Videos” they also allow regular visitors through browsers to unallow auto-started videos. I find it rather suspicious, that they did not mention it within that article.