On my linux system, I have two users. If I log in as user A and use FF and leave a bunch of tabs open, I can view those tabs again later if I restart my computer and log in as user A, so FF remembers its history. No Problem Scenario Logged in as A - open FF - open a bunch of tabs - CLOSE FF log out of A log in as B - do stuff log out of B log in as A - open FF; all the tabs are there Problem Scenario Logged in as A - open FF - open a bunch of tabs - leave FF open (don't close FF before...) log out of A log in as B - do stuff log out of B log in as A - open FF; all the tabs are GONE If I run into the Problem Scenario, I can sometimes use these steps to get the history/tabs back. https://support.mozilla.org/en-US/kb/how-restore-browsing-session-backup Whether the steps work or not, the Problem Scenario is annoying. I don't know what causes this. My desktop manager is KDE.