Auto-play videos suck. They use bandwidth, and their annoying sounds get in the way when you’re listening to music and open a web page. I happen to write for a website that uses them, and it annoys me to no end. (My editors have no control over those auto-play videos, alas.)
But you can stop auto-play videos from playing on a Mac. If you use Chrome or Firefox, it’s pretty simple, and the plugins below work both on macOS and Windows; if you use Safari, it’s a bit more complex, but it’s not that hard.
Auto-play videos are so user-hostile that there ought to be a way to turn them off without needing an extension or hidden developer preference.