See answer above Check http://www.youtube.com/html5 that it is enabled if applicable. Html5 player test videos can be found at http://www.quirksmode.org/html5/tests/video.html if you are not sure where to find a video that will show the "play speed" context menu. If you believe that a html5 video stream is available for the web page but are still seeing the flashplayer video you need to temporarily disable flash support before loading the web page. For that, you may like to try the quickjava addon , which gives you a button to turn flash on/off while browser is running. If you don't see any video after disabling flash then that page does not support an alternate html5 player stream.