Alas, this flag only prevents video that has sound from auto-playing. It’s the inadequate option that my earlier comment was referring to.

Here’s more: https://www.chromium.org/audio-video/autoplay

https://developers.google.com/web/updates/2017/09/autoplay-p...

Quoting the blog post, Google’s decision that ”Muted autoplay is always allowed” is the problem. If any other Chrome users wondered why videos now auto-play without sound (even with this option set), at least based on the relatively minimal docs about this flag, this is why.

It doesn't always work. I have that flag enabled and still encounter videos that autoplay.

Note that Firefox' autoplay blocker breaks some video sites because the Javascript assumes the video is playing when it really isn't. However, with Firefox, videos never autoplay. Chrome's autoplay does not always work, but it doesn't seem to break sites.

I can't seem to find the issue, but in the Safari issue tracker, the point was made that given the way HTML5 video and APIs work, it is impossible to reliably prevent autoplay without breaking some sites. It seems that Firefox went for "reliably prevent autoplay" while Chrome went for "without breaking sites".

FWIW, I switched from Chrome to Firefox because of the autoplay issue.