yes you need 5 windows

By default Firefox can only reopen three closed windows via "History -> Recently Closed Windows/Tabs". This undo/reopen feature is controlled by prefs on the about:config page.

There is are prefs on the about:config page to set how many items to keep in Recently Closed Windows/Tabs.

• browser.sessionstore.max_tabs_undo
• browser.sessionstore.max_windows_undo

You can open the about:config page via the location/address bar. On the warning page, you can click "Accept the Risk and Continue" to open about:config.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Note that 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".

By default Firefox can only reopen three closed windows via "History -> Recently Closed Windows/Tabs

Thanks for this, I appreciate a straight answer. But just to place my gripe on the record, and this is not aimed at the hero cor-el so much as the dev community at large; I've been using Firefox for literally as long as it's existed, and until today I've NEVER heard of a 3 window restore limit, let alone had it affect me. IMO this seems like a newer feature that was and is very arbitrary and inconvenient. In fact it down right pissed me off. Now I've lost progress on multiple projects for work & personal life that I organize by windows. NOT COOL!

If you restore the session automatically and previously used Quit/Exit to close this session and didn't close one window at the time then there is no limit to reopening windows. The limit comes when you try to reopen closed windows via "History -> Recently Closed Windows/Tabs".

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox Title bar, especially if you have multiple windows or Private Browsing windows open to prevent losing tabs in unnoticed windows.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit