Hi Barryng, these hidden settings have evolved in preparation for being added to the Permissions section of the Preferences page in a later release. For now, you'll still need to use about:config. The old '''media.autoplay.enabled''' preference has been replaced by several new ones (you may see it, but Firefox ignores it). Please 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: '''''Block autoplay by default''''' * Double-click the '''media.autoplay.default''' preference and set it to '''1''' * ''Some people suggest you also:'' Double-click the '''media.autoplay.allow-muted''' preference to switch the value from true to false => ''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 '''''Allow autoplay by default''''' (default for Release) * Double-click the '''media.autoplay.default''' preference and set it to '''0''' (or right-click > Reset) I'm sure we'll learn more about the interaction of these various preferences and what sites can bypass them as more users begin to run Firefox 63.