Maybe he's talking about reader view which, for me, can be enabled with F9 or clicking the icon in the address bar (https://support.mozilla.org/en-US/kb/firefox

Maybe he's talking about reader view which, for me, can be enabled with F9 or clicking the icon in the address bar (https://support.mozilla.org/en-US/kb/firefox-reader-view-clutter-free-web-pages https://support.mozilla.org/en-US/kb/firefox-reader-view-clu...)