As of Firefox 100, Firefox follows the system setting on Windows 10-11: System Settings > Accessibility > Visual Effects > Always show scrollbars If you only want to change Firefox, or if you are on Windows 11, you can flip this preference instead: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. ''More info on about:config:'' [[Configuration Editor for Firefox]]. ''The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.'' (2) In the search box in the page, type or paste '''overlay-scrollbars''' and pause while the list is filtered (3) Double-click the '''widget.windows.overlay-scrollbars.enabled''' preference (or click the toggle button toward the right end of the row) to switch the value from true to false. ''You can ignore the preference with gtk in its name, that is for Linux users.'' I can't recall whether you need to do a regular exit/restart of Firefox, or whether that takes effect in every new window (Ctrl+N) immediately. Success?