I understand that vimeo playback is not working for this videos and others on Firefox for Desktop. I took a look at the video player that they use and they are using the JWPlayer that uses [http://www.jwplayer.com/tech-specs/] It auto detects Flash and HTML5 which is strange. Please check to see if these plugins are enabled for this site by clicking on the urlbar icon that looks like a grey box/puzzle piece and make sure it is enabled. Please also make sure that these are up to date: [[Upgrade your graphics drivers to use hardware acceleration and WebGL]] And if we need to take a look deeper in the javascript api, the only warning I saw was: An unbalanced tree was written using document.write() causing data from the network to be reparsed. For more information https://developer.mozilla.org/en/Optimizing_Your_Pages_for_Speculative_Parsing Which is irrelevant.