Along with the Standard and High Quality formats, YouTube offers a High Definition 720p MP4 format version of some videos. By using a bookmarklet, you can easily download these videos to your computer without the use of any other software. Once you have the video downloaded, you simply rename the file and it’s set to go.
1. Open your Firefox web browser.
2. Right-click the Bookmarks Toolbar.
3. Select New Bookmark.
4. In the Name textbox, input a name for your bookmarklet, such as YouTube HD.
5. In the Location textbox, input the following:
javascript:window.location.href = 'http://youtube.com/get_video?video_id=' + swfArgs['video_id'] + "&fmt=22" + "&l=" + swfArgs['l'] + "&sk=" + swfArgs['sk'] + '&t=' + swfArgs['t'];
6. Click the Add button.
When you are viewing Videos at YouTube, you can click this bookmarklet to download the High Definition version of the video you are viewing (if available).
To download Standard or High Quality formats, use this bookmarklet.
Note: the credit for the great javascript behind the bookmarklets goes to Lawrence Albert at Unlock for This
