Question is a bit vague as to what "H264" you are referring to. It is my understanding that the '''OpenH264 Video Codec provided by Cicso Systems, Inc''' '''''plugin''''' is only used for the Hello feature in Firefox. I believe everyone gets that upon installation of Firefox. If you are referring to this extension which is listed in your More System Details > Installed Extensions - https://addons.mozilla.org/en-US/firefox/addon/h264ify/ - the developer has this listed as his Support Site - https://github.com/erkserkserks/h264ify-firefox Few user reviews and few users showing for that extension. Maybe this support ticket might be helpful for you. https://github.com/erkserkserks/h264ify-firefox/issues/3 Sorry, don't use that extension myself, but I thought I'd see if I come some up with an answer for you rather than this thread go too long without an answer.