Hopefully they were not private windows, since Firefox doesn't save information for private windows.

You said you looked here, but are sure none of the windows you remember being open ended up on the closed windows list::

• "3-bar" menu button > Library > History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)
• (menu bar) History > Recently Closed Windows (and within each restored window, Recently Closed Tabs)

Back Up All Session History Files

Do not exit Firefox, or if you closed it, don't re-open it.

(1) To open your profile folder...

If Firefox is still running:

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

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

In the first table on the page, click the "Open Folder" (or "Show in Finder") button.

If Firefox is closed:

Type or paste the following into the Windows Run dialog or the system search box and press Enter to launch Windows Explorer:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, do you see a semi-randomly-named folder? If so, click into it. If you find multiple such folders, find the one that was most recently updated.

(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
• some old .js files from Firefox 55 or earlier

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

To preview the contents of a file, you can drag and drop it onto this page, then click Scrounge URLs: https://www.jeffersonscher.com/ffu/scrounger.html

That tool is on my site, so please let me know if it doesn't work for you.

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar to avoid losing open windows.

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

Nothing helped :( Thanks anyway My windows were open from a long time ago, months ago and today it has some problem and they just dissapeared and that was it

Your sessionstore-backups folder doesn't have any contents older than today? It certainly should, unless you just used "Clear Recent History" to clear history (session history is history).

Is it possible you are not in your regular profile or that your Firefox performed a Refresh?

If Firefox performed a Refresh, you would expect to find your old profile folder on your desktpo inside a folder named Old Firefox Data. Anything like that?

If you had a crash and Firefox found your profile locked and created a new one, you may be able to switch using the about:profiles page (type or paste that internal address into the address bar and press Enter to load it). Because it may not be obvious what is what, resist the temptation to delete anything on this page. You can take a peek into any other profile by clicking the "Launch profile in new browser" button. To make a permanent default profile change, there is a separate button.

Anything there yet? If not, please do a normal shut down and restart of Windows to release file locks and complete pending updates. Then we can move on to the last resort.

No. Nothing happen. Tried everything and tried what I know but nothing. They cant be in History because they are opened, was opened, from a long time and everytime and opened and closed and opened and closed the Firefox, they were there, every window appeared but yesterday they vanished. In History I have other things I opened and closed in the time but not and these. I had them from a long time and they cant be on the History. Well thank you for your try I guess I will try to remember what I had but.. They were so many.. Anyway, thanks

Hi Iceni99, if you did want to look further, the next two things to check are:

(1) Did Firefox orphan your old profile folder?

Here's how to check whether there are additional profile folders in the standard location in addition to the one you're using, but not listed in about:profiles. Start by opening your current Firefox profile folder using either:

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

In the first table on the page, click the "Open Folder" button, to launch a new window listing various files and folders in File Explorer.

In the File Explorer address bar, click the capitalized word Profiles to move up one level in the folder hierarchy. More than one folder here by any chance? Do the files in those folders look like they were last updated around the time of the update?

If you've got any promising looking folders, we can discuss next steps to recover use of them, and any bookmark backup or other useful data files they contain.

(2) Can you recover session history files from a restore point?

Please do not use the Windows Session Restore feature; that can lead to worse problems. However, you can use a utility program to look inside the snapshot data used by that feature and pull out interesting files. Here are the steps:

(a) Set Windows to show hidden files and folders:

https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files

(b) Download and run one of these two programs:

• System Restore Explorer: http://nicbedford.co.uk/software/systemrestoreexplorer/
• ShadowExplorer: http://www.shadowexplorer.com/

Within the most recent restore point shown in the program, you can explore along this path to see whether you can find a shadow copy of your profile:

\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles\

(c) Check in the sessionstore-backups folder for older backups. You can export interesting files to a convenient location such as your currently live desktop. Then you can use the Scrounger tool to view their contents.

Anything interesting?