-> Tap ALT key or press F10 to show the Menu Bar

-> go to Tools Menu -> Clear Recent History -> Time range to clear: select "EVERYTHING" -> click Details (small arrow) button -> place Checkmarks on Browsing and Download History -> click Clear Now

If you want Firefox to automatically Clear your Browsing history when you close Firefox, do this:

-> go to Tools Menu -> Options -> Privacy -> History section -> Firefox will: select "Use Custom Settings for History" -> REMOVE Checkmark from "Permanent Private Browsing mode" -> place CHECKMARKS on:

1) Remember my Browsing History 2) Remember Download History 3) Remember Search History 4) Accept Cookies from sites -> select "Exceptions..." button -> Click "Remove All Sites" at the bottom of "Exception - Cookies" window

  4a) Accept Third-party Cookies -> under "Keep Until" select "They Expire"

-> place CHECKMARK on CLEAR HISTORY WHEN FIREFOX CLOSES -> click Settings... button -> place Checkmarks on the Options you do not want Firefox to remember -> click OK

-> click OK on Options window

Check and tell if its working.

You can (temporarily) set the pref browser.sessionstore.max_tabs_undo to 0 to clear the "Recently Closed Tabs" list.

If you want to re-use the "Recently Closed Tabs" feature (Undo Closed Tabs) then you can reset the pref browser.sessionstore.max_tabs_undo to the default value via the right-click context menu.

• http://kb.mozillazine.org/browser.sessionstore.max_tabs_undo

To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.

• Use the Filter bar at to top of the about:config page to locate a preference more easily.
• Preferences that have been modified show as bold(user set).
• Preferences can be reset to the default or changed via the right-click context menu.

I know all of the previous advice but I don’t want to have to clear everything or quit Firefox to get rid of the recently closed tabs. I want disable this feature permanently as I feel that it is a major security risk.

If you do not want to be able to reopen closed tabs then you can set the browser.sessionstore.max_tabs_undo pref to 0 on the about:config page. This won't work for closed windows because Firefox always keeps at least one closed window in the recently closed windows list if the browser.sessionstore.max_windows_undo pref is set to 0.

Hi WhatTheF,
You're replying to a thread that is around 10 months old. You should use https://support.mozilla.org/en-US/questions/new where volunteers can get more details about your setup.

Because this thread is so old and more people might start using it for their own questions, I'm going to lock it.