Firefox 45 tries to play stand-alone MOV files in the HTML5 video player but cannot decode older MOVs. This script detects URLs ending with .mov and injects a QuickTime player object into the tab to play the video.
Local MOV Files If you want to enable this for local files (files that show file:/// in the address bar), you need to allow Greasemonkey for file:/// URLs generally. Here's how:
In a new tab, type or paste about:config in the address bar and press Enter or Return to load that internal page. Click the button promising to be careful.
In the search box above the list, type or paste greas and pause while the list is filtered
Double-click the extensions.greasemonkey.fileIsGreaseable preference to switch it from false to true