It's not an Issue.
Just an information for Firefox users.
Because of HTML 5 Firefox supports watching .mp4 files in its own UI.
To watch using your video player external to Firefox it is necessary to change a setting in about:config
See here: https://support.mozilla.org/mk/questions/1270887
Search for the parameter: media.play-stand-alone
Change to: false
Firefox MP4 External Player
It's not an Issue. Just an information for Firefox users. Because of HTML 5 Firefox supports watching .mp4 files in its own UI. To watch using your video player external to Firefox it is necessary to change a setting in about:config See here: https://support.mozilla.org/mk/questions/1270887 Search for the parameter: media.play-stand-alone Change to: false