Hello, you can set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. Adjust its value in 0.1 or 0.05 steps (1.1 or 0.9; you might need large value above 1.5 or 2.0) until icons or text looks right. Modifying layout.css.devPixelsPerPx affects user interface and webpages (global zoom) Firefox has a Zoom section in Options/Preferences to set the default zoom level for webpages in case toy need to correct this after modifying layout.css.devPixelsPerPx. Options/Preferences -> General -> Language and Appearance -> Zoom You can open the about:config page via the location/address bar. You can click the button to "Accept the Risk and Continue".