To disablePANGO you need to ensure that firefox is started with MOZ_DISABLE_PANGO=1in its environment. One way is to add a ".sh" file to/etc/X11/xinit/xinitrc.d/ which will be sourced at X11 startup.For example: /etc/X11/xinit/xinitrc.d/moz-disable-pango.sh # Disable the PANGO text renderer in Mozilla MOZ_DISABLE_PANGO=1 export MOZ_DISABLE_PANGO