Before your update did you have it were it saved the sessions and history and cache option unchecked so they wouldn't not be cleared. And usually on bad crashes things will be lost as opposed to hard restart where it can be recovered. And sounds like the worse case happened and everything was wipe cleaned from the crash. If this is the case there is no way to find or recover them.

Hi RuthiB, usually Firefox will attempt an automatic crash recovery for a regular (non-private) session. Could you check whether either of these are available (not grayed out):

• "3-bar" menu button > Restore Previous Session
• (menu bar) History > Restore Previous Session

If they are grayed, check either:

• "Library" toolbar button > 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)

If that doesn't help...

Firefox creates numerous session history files, but because session history is only for the immediately previous session, it is unfortunately too easy to lose it. Could you start by making a backup of your existing session history files? Here's how:

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 > "?" button > 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
• various .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/res/scrounger.html

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

Thanks Jefferson!! That worked like magic! :)

I now understand what happened - the crashed closed my session and then either the reboot or the update changed the setting from where a new session starts with restoring the previous one back to the default (?) of opening a blank page. So I just got the blank page and no 'recently closed windows' were available, probably because the computer had to restart (cause of the crash).

Since I tried to figure out what happened (and needed to get some work done) my "last session" was not the one that I wanted to restore any more. Which is where your nifty tool came in and could use the "upgrade" file, which of course coincided with the last session as the upgrade and crash happened more or less at the same time! :)