from https://support.mozilla.org/en-US/questions/1238026

Hi, the settings have evolved. The old media.autoplay.enabled preference has been replaced by several new ones. Let's give this a try: (1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk. (2) In the search box above the list, type or paste autop and pause while the list is filtered To set your preferred behavior: Allow autoplay by default (default for Release)

• Double-click the media.autoplay.default preference and set it to 0 (or right-click > Reset)

Block autoplay by default

• Double-click the media.autoplay.default preference and set it to 1

=> Does that work for you? Ask on a site-by-site basis (default for "Nightly")

• Double-click the media.autoplay.default preference and set it to 2
• Double-click the media.autoplay.ask-permission preference to switch the value from false to true
• Double-click the media.autoplay.enabled.user-gestures-needed preference to switch the value from false to true

I'm sure we'll learn more about the interaction of these various preference and what sites can bypass them as more users begin to run Firefox 63.

The fix provided partially worked. I made sure every setting listed was set as posted above. However this yahoo plays a vids with audio.

https://www.yahoo.com/entertainment/caitlyn-jenner-changed-mind-trump-cannot-support-anyone-working-lgbtq-community-210743586.html

So as it stands, the solution is a partial fix. It stops some vids, but not all. Pre 63 solved it solid. I just do not understand why sites force (non advertising) video autoplay on end users.

That Yahoo video seems to trigger on scrolling and/or mouseover, which might not technically be considered autoplay, although it's very annoying. Another reason to avoid Yahoo.

As a defense until someone finds a better workaround, you might try one of the muting extensions so even if the video starts it doesn't destroy your eardrums.

• https://addons.mozilla.org/firefox/addon/mute-sites-by-default/
• https://addons.mozilla.org/firefox/addon/auto-mute/
• https://addons.mozilla.org/firefox/addon/mute-tab-webextension/

Well I have no real other alternatives to yahoo as I do not support google, facebook or witter. But thank you! I will clear this trouble. Also, thank you so much for putting up with my problem and helping.

Every other site respects my autoplay settings (all of them, as they currently exist). No site, except news.yahoo.com autoplays video with sound. Only Yahoo! News plays it. Besides the numerous settings where it's disabled I have explicitly disallowed it on all of Yahoo's sites, individually- yet it still autoplays! (Privacy & security | For websites that autoplay sound - I have blocked exceptions for all of Yahoo's sites).

When I scroll down a page after having paused the video at the top of the page, then I scroll back up to the top, which displays the video area- it starts again!

Here's an example: https://news.yahoo.com/twitter-users-troll-trump-hilariously-103701689.html

@ Mozln I have the same problem. Nothing is stopping the autoplay on yahoo. The solutions provided above is as a good as it got, in short, no stopping auto play on yahoo news. Eventually someone will figure it out. I run my PC w/o sound but I feel sorry for ppl with data plans that get eaten alive by this crappy behavior of websites and their vid autoplay.

<yes, I realize these are instructions on a very old system and version ... it might possibly have some use on more modern configurations as well though>

To stop Yahoo autoplay in Windows 7 w/ Firefox 56 ...

As noted above, goto about:config ... search for "autop" ...

Where two entries are returned ... media.autoplay.enabled and media.block-autoplay-until-in-foreground

First, change media.block-autoplay-until-in-foreground to false then change media.autoplay.enabled to false then change media.block-autoplay-until-in-foreground back to true that's it. That worked for me 4-8-19.

The Boolean pref media.autoplay.enabled no longer exists in current Firefox releases and has been replaced by the Integer pref media.autoplay.default (0=Allowed, 1=Blocked, 2=Prompt).

• https://support.mozilla.org/en-US/kb/block-autoplay