Our internal site has a page that displays a video via an embedded object the Quicktime plugin. The video source in the page might be "/sample.mov", and is standard H.264, delivered with Content-type of "video/quicktime". Firefox has had its Applications settings set to handle this with the Quicktime plugin. The page works fine both with Firefox 45 and previously - the Quicktime plugin plays the movie. If you retrieved the "/sample.mov" URL directly in Firefix <45, it also worked as expected, with Firefox using Quicktime to play the video. However, with Firefox 45, Firefox uses its own video player for the URL-based request, not Quicktime. Presumably for some reason the Application setting for "video/quicktime" is now being ignored. I'm not sure if this was a deliberate change or some sort of unintended side effect. I just wanted to see if anyone could shed any light on this before digging in further? FWIW, this is Firefox 45.0.1 (32 bit) on Windows 7, with various versions of Quicktime from 7.7.4-7.7.9. I know Firefox 43 did the "right" thing and used the Applications setting in the direct URL case. I know plug-in support is on the way out, but until then this is unfortunate, since the Quicktime plugin supports single-frame advance and is preferred here for our purpose while still possible.