There are two preferences in about:config. If you haven't edited that previously, open a new tab and enter about:config in the address bar, accept the risk and search for menuA. To stop the menu being shown, change the following preference to 0. In my experience you can still access individual menus by pressing alt + (say) f for File. ''ui.key.menuAccessKey'' There is another preference which is supposed to affect access to individual menus if you don't change that first preference but changing it to false seems to me to do nothing. ''ui.key.menuAccessKeyFocuses'' https://support.mozilla.org/en-US/questions/1368147#answer-1484025 https://support.mozilla.org/en-US/kb/about-config-editor-firefox

''ui.key.menuAccessKeyFocuses'' worked for me, thanks!