There are several possibilities here.

1) You may have switched to an old profile.

Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there?

2) Are you using sync?

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers before using sync again.

Firefox automatically makes backups of the bookmarks. These are stored in the bookmarkbackups folder.

Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Restore. From the list, pick the file you want and click it.

The backups are stored in a jsonlz4 file named something like this; bookmarks-2016-06-29_1424_enD1GTH ya0JmicnYWg4V4g==.jsonlz4

In this example; 2016-06-29 = date created, 1424 = number of entries.

You can check if you have orphaned profiles that aren't registered in profiles.ini and that do not show in the Firefox Profile Manager. You can check that by opening the current profile folder and go up one level.

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

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

In Mac OS X v10.7 and later, the ~/Library folder in the Home directory is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X
• ~/Library/Application Support/Firefox/Profiles/<profile>

FredMcD said

There are several possibilities here. 1) You may have switched to an old profile. Type about:profiles<enter> in the address bar. How many profiles are listed? How many should be there?

---

2) Are you using sync?

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers before using sync again.

I'm unable to decipher the "About Profiles" screen. It states at the top "This is the default profile and cannot be deleted" and there is essentially nothing else on that screen.

And, no, I'm *not* using Sync.

FredMcD said

Firefox automatically makes backups of the bookmarks. These are stored in the bookmarkbackups folder. Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B. Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Restore. From the list, pick the file you want and click it. The backups are stored in a jsonlz4 file named something like this; bookmarks-2016-06-29_1424_enD1GTH ya0JmicnYWg4V4g==.jsonlz4 In this example; 2016-06-29 = date created, 1424 = number of entries.

Looking through the online help pages, I've tried the "Restore" tip - but the only bookmarks that appear are from yesterday, when the problem occurred. There are no json files on my system, other than the one from yesterday. I'm unable to "get at" the supposed backed up bookmarks from a previous time (the day before yesterday).

Did Firefox experience a problem such as a severe crash, or did it get interrupted while performing a Refresh, or did this just occur randomly at startup??

At the risk of repeating some earlier thoughts and apologies for the copy/paste:

There are cases in which Firefox cannot access your existing settings and starts you up in a new profile, which looks like a first-time installation of Firefox. Firefox then may retrieve some old settings by importing them from other browsers on your system.

If you haven't already, before doing any file moves/deletes/reinstalls, you may want to do a normal system shutdown and startup to release any file locks and complete any pending updates. One user reported it took three shutdown/restarts to sort out his issues.

If your data does not magically reappear, the most likely scenarios for complete data loss are:

(1) A Refresh occurred but the migration of data from your old profile to your new profile was incomplete, or
(2) Your old profile was locked, so Firefox ignored it and created a new one

Here's how to investigate those two possibilities:

Did Firefox perform a Refresh?

Unless it was interrupted in progress, you should find a folder on your desktop named Old Firefox Data. Inside would be a semi-randomly-named folder with freshly updated files. Do you see anything like that?

If so, we'll suggest how to rescue key files or completely restore the earlier profile folder.

If not...

Does the Profile Manager list your immediately previous profile folder?

To check on that, inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list all the profiles Firefox is currently aware of. If you see a profile that is not currently set as default that looks promising, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but I think those are still "under construction" so please ignore them.)

Firefox should exit and then start up using the other profile. Is that the right one?

If it's not there...

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. Start by opening your current 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/Return

In the first table on the page, click:

* Windows: the "Open Folder" button, to launch a new window listing various files and folders in Windows Explorer.
* Mac: the "Show in Finder" button, to launch a new window listing various files and folders in Finder.

In the Windows 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?

(Mac users: please do what you need to do in Finder to check up one level...)

If you've got any promising looking folders, we can discuss next steps to recover use of them.