Did you know that you can download videos directly from YouTube without installing extra, YouTube-specific software? In fact, all you need to pull this off, is your browser. That's all. We're going to be taking advantage of a little known thing called browser "bookmarklets". A bookmarklet is similar to a bookmark. Let me show you how to create a bookmarklet that will allow you to allow you to download HD YouTube videos in MPEG-4 format directly from your browser to your PC. Did I mention that this method is also compatible with all modern web browsers? Firefox 3.0+, Chrome 3+, IE7+, etc.
Simply highlight the following code using your mouse and "drag" it into your browser's tab bar:
javascript:window.location.href = 'http://youtube.com/get_video?video_id=' + yt.getConfig('SWF_ARGS')['video_id'] + "&fmt=22&l=" + yt.getConfig('SWF_ARGS')['l'] + "&sk=" + yt.getConfig('SWF_ARGS')['sk'] + '&t=' + yt.getConfig('SWF_ARGS')['t'];
Depending on which browser you are using, your custom bookmarklet will be given a default name such as "Untitled" as is the case with Google Chrome (shown above). Now, no matter which browser you are using, all that is require of you is to locate a YouTube video with a HD option, toggle HD on, and simply click your new bookmarlet and a "Save As" prompt will appear. You will be given the option to name the file and choose the location for it to download to.
If you should happen to want to come across as YouTube video which does not offer the HD option, you can still download the high quality (if this is supported by the video) version using this code:
javascript:window.location.href = 'http://youtube.com/get_video?video_id=' + yt.getConfig('SWF_ARGS')['video_id'] + "&fmt=18&l=" + yt.getConfig('SWF_ARGS')['l'] + "&sk=" + yt.getConfig('SWF_ARGS')['sk'] + '&t=' + yt.getConfig('SWF_ARGS')['t'];
And, if there's a video that you wish to download which does not allow for either HD or high quality viewing, you can always use this code to download standard definition YouTube videos:
javascript:window.location.href = 'http://youtube.com/get_video?video_id=' + yt.getConfig('SWF_ARGS')['video_id'] + "&l=" + yt.getConfig('SWF_ARGS')['l'] + "&sk=" + yt.getConfig('SWF_ARGS')['sk'] + '&t=' + yt.getConfig('SWF_ARGS')['t'];