YouTube was able to develop a way for the browser to cache the videos so they can be seen after closing or reloading the tab / page and this feature is live starting today. The requirement for this is that the video has completely loaded. Try to go to a YouTube video, wait until the video is buffered and then reload the page. You'll notice that the video starts instantly and you can watch it directly from your browser's cache. This works even if you close the tab and open the same page later.Videos will load from the browser's cache even if they're embedded in a web page, so this feature is not limited to YouTube's site.[via googlesystem