How can I rotate a video?
Use QuickTime to Rotate Videos
You don't need to use any 3rd party tools to do this. It's built right in to QuickTime Player.
Any file that can be opened in QuickTime can be rotated by choosing Edit &gt; Rotate Left (or Right) or by typing Command-Shift-L / R.
If you alter a movie file in this way and attempt to close the file (Command-W) you will be prompted to save your changes. Save them to a new file and you will have a newly rotated video.
Share your Video on YouTube with QuickTime
QuickTime also has a built-in way to share your video on YouTube. With the video open (and correctly rotated now) select Share &gt; YouTube...