You may be using the new modal print interface and this new user interface currently doesn't have the "Simplify Page" feature that uses Reader mode. There is a bug created to add this feature to the new interface, but working on this hasn't been started yet. *[https://bugzilla.mozilla.org/show_bug.cgi?id=1666247 Bug 1666247] - Add the Simplify Page checkbox to the new print UI Please do not comment in bug reports<br>https://bugzilla.mozilla.org/page.cgi?id=etiquette.html You can vote for a bug to show your interest<br>https://bugzilla.mozilla.org/page.cgi?id=voting.html ----- Note that for now you can revert to the previous interface by setting a pref to false on the <b>about:config</b> page. *print.tab_modal.enabled = false You can open the <b>about:config</b> page via the location/address bar. You can click the button to "Accept the Risk and Continue". *https://support.mozilla.org/en-US/kb/about-config-editor-firefox