Updates to codecs for Quicktime Player

QuickTime includes the most commonly used codecs with each install. When you encounter a file that you don't have the proper codec to view you may be directed to the third party component page offered by Apple.
But it doesn't tell you which to install because it doesn't actually "read" the file. It only knows that something is missing.
Best practice would be to use the MOvie Info window on files that give you trouble. You'll be able to view the codecs used in it and need only do a Google search to find what you need.

If you try to open the file with QT and QT does not handle the file you will not be directed anywhere, you will get, Error-2048 the file is not a movie file. QT for windows will only show info in the QT player for files it can handle. You would need to right click on it and choose properties or try
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What happens when I get this error message when the file is a MOV file?
What codec could possibly be missing?

The .mov file extension is merely a container. It can hold dozens of file formats and numerous codecs.
If you're missing the codec (whatever may have been used that is not part of the standard QuickTime install) the .mov file will not play as the author intended.
The Movie Info (Control-i) should show the codecs used.