If you want to remove all toolbars from Firefox in fullscreen mode on Mac, this is the procedure:
about:config:in the location bar to open advanced settings. (If it is the first time you do it, you might have to click "confirm" or something like that in the scary screen that comes up first.)
- search for
full-screen-api.allow-trusted-requests-onlyand double-click the line that is found, so the value changes to
- Bring up the Bookmark Toolbar if you don't have it (menu View -> Toolbars -> Bookmark Toolbar)
- Right-click on empty space in the Bookmark Toolbar, and select New Bookmark...
- In the Name field, type something like "Enter Fullscreen" (it doesn't really matter, just don't leave it blank)
- In the Location field, enter the following line:
- Click Add to save the bookmark.
Now, there is a bit of a snag. That preference in
FF has a preference,
browser.fullscreen.autohide, that in theory should govern the behaviour of toolbars when going fullscreen. It is set to true by default, meaning toolbars should disappear. However, for some reason this property has (almost) always failed to work on MacOS/OSX builds of Firefox.
There used to be a few extensions that corrected that behaviour, but they've all gone away when Firefox switched to WebExtension APIs, which basically sandboxed extensions more rigidly and blocked them from changing the browser interface as deeply as they could before. This was the price for the dramatic performance improvement seen in Firefox 57+.
Credit to this AskDifferent post where I first found the trick.