QuickTime with Firefox
The recent Firefox automatic update might break many internet plug-ins, and one of them could be your QuickTime plug-in. The result is showing a corrupted file within Firefox browser. There is a simple way to work around it by adjusting some internal setting:
For Windows:
Under Firefox, In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.
In the filter box, type or paste media. and pause while the list is filtered. Double-click media.windows-media-foundation.enabled or media.wmf.enabled to switch its value from true to false.
By doing this it will force Firefox browser to open QuickTime player to play the video.
For Mac/Apple:
Make sure to have QuickTime 7 Player installed. QuickTime Player X comes pre-installed on most Macs but not QuickTime 7. Go here to download and install: https://support.apple.com/kb/DL923?locale=en_US
Under Preference of Firefox: Go to the “Applications” section, set QT file to use Quicktime 7 Player (if it’s not listed there, you can manually select the location for the app: /Application/Utilities/Quicktime Player 7 ) and not the plugin.
Then under Firefox, In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful. In the filter box, type or paste media. and pause while the list is filtered. Double-click media.play.stand-alone to switch its value from true to false.