Tim, I managed to block video Autoplay by doing the following.

• go to the Tools menu (alt+T) and select settings.
• in the settings page, search for "Autoplay".
• find the Autoplay section in the results and press its settings button.
• in the dialogue box that opens, choose "Block Audio and Video" as Default for all web sites.
• press the save button.

(you might need to restart Firefox to see the change)

After doing this, I need to manually start playing a video for it to play.

However, I personally do not know if it is possible to prevent all sites from video looping, via a Firefox setting.

That was my previous setting, but I'll try unsetting and resetting it again. Thanks

Doesn't work for me, but thanks.

You can look at these prefs in about:config to see what settings work for you to block media auto-play.

• media.autoplay.default = 5 [0:allow;1:blockAudible;5:blockAll]
• media.autoplay.blocking_policy = 2
• media.autoplay.allow-extension-background-pages => false
• media.autoplay.block-event.enabled => true
• media.block-autoplay-until-in-foreground

You can open about:config via the address/location bar. You can read the warning and click "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

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