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When you open a video in facebook, you're redirected to mobile version so that it can play in HTML5 player
When you open a facebook video page (will not work if you click on a video and it pops-up) you are redirected to the mobile version of the site where video can be played with an HTML5 player. The desktop version of the site only supports Flash videos unfortunately.
So this script is very dumb but quiet reliable. You need to go to the video page like: https://www.facebook.com/video.php?v=10152484650042694 Usually when you see videos on your timeline, you need to click on the "video" link at the top of the post.
Known issue: When right clicking on a link to video page it does not redirect. Only if page is refreshed or link opened in a new tab/window then it redirects. See issue 2135.
