Firefox uses a JS based fullscreen mode as opposed to the native MacOS fullscreen mode apparently. The result is it looks and “feels” different.
What you can change, is the “feel” of the fullscreen video modes in Firefox. The result of this change is the full screen video will become it’s own space in Mission Control, and you can 4 finger gesture between the spaces, hover to see the top menu, etc. This is what you expect of a fullscreen video in either Chrome or Safari.
You’ll need to
- Navigate into your about:config (type that into the URL bar of Firefox, click past the warning)
- Uncheck the “Show only modified preferences” option
- Search for “full-screen-api.macos-native-full-screen”
- Toggle option to true
There should be no need for a browser refresh and you’ll notice the difference upon the next video you expand to full screen. Also the dialog text “website has entered fullscreen” can’t be changed which bothers me also.