You have no closed windows listed under:

• "3-bar" menu button > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

Unless there is some bizarre transient glitch, it sounds as though you might be using private windows. There is a way to run Firefox 100% private with no closed window history retained. If you could check:

Settings page > Privacy & Security panel > History

The "Firefox will:" selector will point you to the status:

• Firefox will: remember history => all is well
• Firefox will: never remember history => this is a problem
• Firefox will: use custom settings for history => review the checkboxes and make sure you do NOT use automatic private browsing and that you DO remember browsing history

Another possibility is that the window isn't closed but somehow moved off-screen. If you look at the Firefox button on the Taskbar, does it show any additional windows?

You have no closed windows listed under:

• "3-bar" menu button > History > Recently Closed Windows
• "Library" toolbar button > History > Recently Closed Windows
• (menu bar) History > Recently Closed Windows

Unless there is some bizarre transient glitch, it sounds as though you might be using private windows. There is a way to run Firefox 100% private with no closed window history retained. If you could check: Settings page > Privacy & Security panel > History The "Firefox will:" selector will point you to the status:

• Firefox will: remember history => all is well
• Firefox will: never remember history => this is a problem
• Firefox will: use custom settings for history => review the checkboxes and make sure you do NOT use automatic private browsing and that you DO remember browsing history

Another possibility is that the window isn't closed but somehow moved off-screen. If you look at the Firefox button on the Taskbar, does it show any additional windows?

No windows listed there. I'm not using private windows, and there's nothing in the task bar. It's not in the second desktop either. I do have firefox set to delete history when I close firefox, but I did not close it, and theres tabs I closed earlier today that do show up in the recently closed section. That's why I'm so confused, it should be there, but it's not

Could you grab a backup of your existing session history files? Here's how:

(1) To open your profile folder...

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, find the Profile Folder row and click the "Open Folder" button. This should launch Windows' File Explorer listing the contents of your current profile folder.

(2) Copy out session history files

In your profile folder, double-click into the sessionstore-backups folder. Save all files here to a safe location such as your Documents folder.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.jsonlz4: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.baklz4: a backup copy of recovery.jsonlz4
• previous.jsonlz4: the windows and tabs in your last Firefox session
• upgrade.jsonlz4-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

Sometimes you can tell from the last modification time which one will have your missing tabs, but not always.

Optional File Contents Preview

These compressed files are a pain to view, so I created a tool on my website to list out their contents. If you want to try that, you can drag and drop it onto the large box on the following page, then click the "Scrounge URLs" button (keep the checkmark for the "Include closed windows" option):

https://www.jeffersonscher.com/ffu/scrounger.html

If you don't get a list within 15 seconds, that probably means the script is caught in a loop. You may need to close the tab to avoid a tab crash and then try again in a new tab.

If you get a useful list, use the "Save List" button to archive it as a web page of clickable links for future reference, in case no other approach is successful.