You can look at these prefs on the <b>about:config</b> page to see what settings work for you. You probably at least need media.block-autoplay-until-in-foreground = falsecreate an allow audio and video exception for YouTube if you currently block A/V. *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 the <b>about:config</b> page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue. *https://support.mozilla.org/en-US/kb/about-config-editor-firefox ---- *https://support.mozilla.org/en-US/kb/block-autoplay