I learned today that tools like Firebug won’t display the headers on a file that would normally be downloaded (as opposed to say, displayed in a browser). The solution? The command line, of course. I wanted to make sure a web server was setting the right MIME type for an mp4 video.
curl -I http://path.to/videos/vid.mp4
This will just show the headers, including
Content-type, which is the MIME type.