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