Hello there, to complete this, follow these steps below; 1) paste "about:config" into your URL bar. 2) search "autoplay" 3) set that value to false (basically disabling the AutoPlay for media.

Note : setting 'media.autoplay.enabled' to ' false' can cause problems.

Best to do this :

Type in the address bar about:config (press Enter) (promise to be careful, if asked) Type and look for the preference : media.block-autoplay-until-in-foreground and set its value to false

Thank you for the responses. I changed the media.block-autoplay-until-in-foreground to True (it was false, and because I do want that feature blocked, I changed to to true), and the media.autoplay.enabled to False (was true). I may have problems, hopefully they won't be as bad as having to constantly mute &/or change tabs to stop an auto play video!

Teling you to change 'media.block-autoplay-until-in-foreground' to
'false' was a dumb mistake - I apologize  ! Good for you to have figured it out - well done  ! I sure hope that changing the values of these prefs will solve your
problem  !

With version 57 nothing seems to work, any longer. Videos in most cases play once you get to them, unless manually turned off. Anyone find a way to turn them off, short of using another browser? I have turned all plugins for video to "never activate" to see if that would stop videos. It did not.

I've gone in to the about:config file to change settings based on various posts and nothing has worked. I am waiting for NoScript 10 to be released, which will hopefully give control back to the user instead of the web designer. In the meantime I will continue to avoid some websites that overload the videos, I don't want to waste my time turning off manually.

Would you please do this :

3-bar menu (or 'Tools') => Add-ons => Plugins

Make sure that Shockwave Flash is set to 'Ask to Activate'

Hi, thanks for the suggestion, but I had initially set it to "Ask to Activate," when that didn't work, I set it to "never activate." That also didn't work.

Apparently Mozilla does not listen to subscribers and fix the problem of automatically starting of videos. The online help “fixes” do not work.

Maybe you'd like to give this add-on a try :

https://addons.mozilla.org/en-US/firefox/addon/policy-control/

This part here actually worked: I changed the media.block-autoplay-until-in-foreground to True (it was false, and because I do want that feature blocked, I changed to to true), and the media.autoplay.enabled to False (was true). There are some videos that will not play at all, but seriously I'd rather have some of them not play than have them all autoplay.

lkbart said

This part here actually worked: I changed the media.block-autoplay-until-in-foreground to True (it was false, and because I do want that feature blocked, I changed to to true), and the media.autoplay.enabled to False (was true). There are some videos that will not play at all, but seriously I'd rather have some of them not play than have them all autoplay.

Well, good for you  ! What took you so long  ?