''<p>Me [[#question-1415403|said]]</p>'' <blockquote>How do I stop firefox from preventing my mac from shutting down? All other open apps are closed and data and settings saved automatically by apple when i hit shut down but firefox just stays open and prevents shutdown until i close it manually. </blockquote> Not sure if this is indeed the cause however. from https://support.mozilla.org/en-US/questions/1415293#answer-1584446 <blockquote>'''On Mac closing Firefox can be more complicated because you can close all open windows, but keep Firefox running with the menu bar visible or minimized in the Doc.''' Make sure to use "Quit Firefox" with all windows still open, especially if you want to use "Restore Previous Session". Otherwise check "History -> Restore Previous Session" and "History -> Recently Closed Tabs/Windows". </blockquote>

Are you using "Clear history when Firefox closes" ? *https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox