Look on your desktop. Do you see a folder called; Old Firefox?

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

You can check if you have an orphaned profile that isn't registered in profiles.ini and that does not show in the Firefox Profile Manager. You can check that by opening the current profile folder via the about:profiles page and go up one level to see if there are profiles present that didn't show on the about:profiles page.

• http://kb.mozillazine.org/profiles.ini_file

If you have found an orphaned profile then you may want to recover some personal data.

"System Recovery" can take a number of different forms. If you used a built-in feature of Windows 10, you may find your old data located in this temporary folder (removed after 28 days, so check ASAP):

C:\Windows.old

Can you find a folder like that on your computer? If so, in order to see whether your old Firefox data is in there:

(1) Set Windows to show hidden files and folders. This article has the steps:

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

(2) Click through to this folder:

C:\Windows.old\Users\your-user-name\AppData\Roaming\Mozilla\Firefox\Profiles

The Profiles folder might contain only one semi-randomly-named folder, or multiple folders. If there's only one, click into that one, if there are multiple folders, you can check each one.

Inside the semi-randomly-named profile folder, look for a folder named bookmarkbackups and click inside. Here you would expect to find files with names similar to:

bookmarks-2017-08-29_3456_gibberish==.jsonlz4

The data coded into the file name shows when the file was captured, and the number that follows is the number of bookmarks and bookmark folders recorded in the backup.

This file is compressed, and not human-readable. However, it can be restored to your current Firefox in place of the bookmarks you see there now. To do that:

(A) Copy the backup file to your Desktop or another convenient location. For example:

right-click the backup file > Copy

Go to your Desktop, right-click a blank area > Paste

(B) Inside Firefox, use the Restore menu, Choose File command, to point Firefox to your desktop and grab the old backup file. This article has more details on the Restore feature: Restore bookmarks from backup or move them to another computer.

Hope that helps.

Mike17 said

I had thousands of things bookmarked at Firefox, then had to do a System Recovery, which forced me to create a new Firefox account. This one has no bookmarks at this point. Can I somehow retrieve the bookmarks from my old account?

Did you ever set up the Sync service before, to copy your bookmarks and other selected Firefox data to Mozilla's servers? In order to reconnect with your old Sync data, you would need to use the email address and password of your old Firefox account rather than create a new one. Also, you really do need to know the password, otherwise you can't access the old Sync data.

OK, I found the old bookmarks file. It now stands as an endless black and white page, with all the links in blue. I can click on them and get to the sites, but I can't delete anything. Is there a way to make this list more workable? I'd love to add it to my current Firefox bookmarks. Thanks.

What is the name of that file?

Mike17 said

OK, I found the old bookmarks file. It now stands as an endless black and white page, with all the links in blue.

That does not sound like one of Firefox's automatic backup files. They are compressed files that look like gibberish if you open them in a tab.

FredMcD: file:///C:/Users/Main/Documents/bookmarks.html

If that are clickable links then that could possibly be an HTML backup and such a backup needs to be imported.

• Bookmarks -> Show All Bookmarks -> Import & Backup -> Import Bookmarks from HTML

Try what cor-el said.