Firstly, blocking autoplay has been a feature since Firefox 66 and it's not new for version Firefox 67. For more information about this feature, see Allow or block media autoplay in Firefox.

Secondly, the issue you are having seems completely unreleased to the autoplay feature.

Much of the HTML5 video support on Windows comes from the Windows Media Feature Pack. Sometimes things like Windows Update can cause some issues with it, so you may need to redownload the feature pack for your version of Windows.

If it's still not working after restarting your computer, go to the YouTube HTML5 test page and let us know which video codecs are not supported. All of them should be, but sometimes the MSE & WebM VP9 codec can be unsupported. That's not an issue.

Hope this helps.

Hi Wesley,

After the update to 67.0 there was a headline announcing the autoplay feature and furthermore the Youtube behavior I described and only started after the 67.0 update, the news site was unchanged. I set Youtube to unblock and it's back to normal. News site is set to block and all the videos play, presumably because the sound is muted. I wouldn't know as I keep my audio muted always to avoid the tyranny of such ads.

The point is the feature just blocks sound. What is needed to to block all ad videos.

You can open the YouTube test page to check support in Firefox for playing HTML5 media.

• https://www.youtube.com/html5

See also:

• https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows
• https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues
• https://support.mozilla.org/en-US/kb/html5-audio-and-video-firefox

There seems to be a mus-understanding here.

Youtube is just fine (now). It was being blocked because the sound was not muted.

The problem is this:

"The point is the feature just blocks ads (with un-muted) sound). What is needed is to block all ad videos."'