You can disable autoplay in Firefox by setting the following about:config prefs:

  media.autoplay.enabled = false
  media.autoplay.enabled.user-gestures-needed = true

This feature is not currently enabled because it can confuse some websites' video players. They can get stuck in a bad state because their JavaScript assumes the video is playing, but because Firefox didn't autoplay it the player buttons don't work correctly.

I hate these decisions by Firefox where they don't enable something because it would be inconvenient for websites! They should enable it and websites should fix their broken players.

Then their naive users would abandon them en masse because Facebook and YouTube won't work right. The thing to hate is that useful settings like this aren't in a more readily accessible preferences dialog for the rank and file to discover. You have to be told it's there or go spelunking through about:config.

> Meanwhile, Google still hasn't added a way disable auto-playing videos (regardless of whether a video is muted) in Chrome.

This bit is especially infuriating for me, as there seems to be a High Sierra issue with Chrome and videos (for me, at least - it's hard to figure out how widespread it is). They cause massive browser lag when they're on a page for me, to the point of missed characters while typing.

I use Iridium for this and other things: https://github.com/ParticleCore/Iridium

I tried setting the Autoplay policy at the browser level once but found that it was inconsistent and broke certain players. Iridium works perfectly.

There is supposedly a way. On Chrome 63 and newer, you can set "Document user activation" in chrome://flags/#autoplay-policy & relaunch.

However, it does not seem to do much, if anything, for me. I tend to just use Privacy Badger to block any site that looks like a CDN

> you can set "Document user activation" in chrome://flags/#autoplay-policy & relaunch.

That won't fix the problem of auto-playing video on CNN or other sites that are not YT. Trying to read news from CNN is still a matter of waiting for the page to load, then wait for the video to load and start playing, then click on the pause button, and voila you can read in peace.

Chrome has that also.

Go to chrome://flags, search for Autoplay policy, and select Document user action is required.

Note that if you use the Imagus extension, this could block some videos/gifs/etc from playing when you hover over a link.

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.