OS: Catalina Model: iMac (27-inch, Late 2013) (tested on Macbook pro 2018 and 2011 too) Firefox: 84.0.2 Expected functionality: First expand the window to full screen using the green window control. The expectation is that the tab and tool bars will eventually hide, however firefox implements this - by sliding up when scrolling or just sliding up and autohiding after a short time. The tab bar should then reappear when the mouse move to the top of the screen. Functionality Observed: Tab and tool bars never autohide. They are always there. The only way to that they hide is when a video (YouTube, Netflix) fullscreen controls are selected. Otherwise they are there on every page and that is not the expected behavior. Id like every page to autohide the top bars (similar to what all tablet/mobile device browsers do). Settings verified: browser.fullscreen.authide= true (see image). Hide toolbars is checked (see image). Issue I have found posted on this do not provide a concise reason as to why this behavior exists when all settings are properly set.