When you restarted Firefox, did you get any unusual messages?

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 started 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 the "Open Folder" button, to launch a new window listing various files and folders in Windows Explorer.

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?

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

Yes I found a folder called Old Firefox data and it has a file dated the day of the crash. Please advise on what I should do next.

If you want to do a complete "roll-back" to the folder inside Old Firefox Data, I've listed the steps in other threads. For example: I did a Reset of Firefox - How do i get add my 'Old firefox data' back?

If you want to restore some critical data but you don't care about other data, we can help with the steps. This article lists the critical files for different kinds of data: Recover important data from an old profile.

I got down to the Copy Old Data in place of new section and got stuck. It says to delete the contents but what I am seeing are the old data contents. I can't recover it if I delete it. It looks like it is the same info in both places. I can't figure out how to tell where I am with all of the switching back and forth. Very confusing.

Good idea to stop if it's not clear.

The Windows Explorer address bar should be totally different between the two folders:

Your new profile is under

Computer - C: - Users - username - AppData - Roaming - Mozilla - Firefox - Profiles - something random

Your old profile is under either of these:

Old Firefox Data - something random

Computer - C: - Users -username - Desktop - Old Firefox Data - something random

Does that help clarify which window has which contents?

Note: I'm using Windows 7, so Windows 10 may display this differently. If you have your Windows Explorer set up with the folder list in the left pane and the files list on the right, that also should help provide content.

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

You can copy files like these with Firefox closed to the current profile folder to recover specific data. Note that you should be cautious with copying SQLite database files if you previously had problems.

• bookmarks and history: places.sqlite
• bookmark backups: compressed .jsonlz4 backups in the bookmarkbackups folder
• cookies.sqlite for the cookies
• formhistory.sqlite for saved form data
• logins.json and key3.db (decryption key) for Passwords saved in the Password Manager
• cert8.db and possibly cert_override.txt for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other Site Preferences
• sessionstore.js for open tabs and pinned tabs

I saved the old to a thumb drive so I can tell them apart. I thought I successfully changed it but now I can't get in at all. When I click on my Firefox shortcut it says Your Firefox profile cannot be loaded. It may be missing or inaccessible. I am not very tech savvy and I don't understand even half of the info in the last reply. I can't find any of the locations it is referring to and when I create the new profile and the instructions say "leaving that folder open, switch back to Firefox and Exit" I can't get back to the new profile to copy anything in. I need instructions for a novice.

If Firefox cannot find your profile, it's possible that in the process you changed the name of the folder that Firefox is looking for. Please start Firefox using the Profile Manager and select any existing profile to get up and running again:

Either:

• Call up the Windows "Run" dialog using the keyboard shortcut: Windows key + R
• Click in the Windows 10 search box (may be on the Task bar)

Type or paste the following, then press Enter to execute it:

firefox.exe -P

That should call up the profile manager.

Don't delete anything here!

To start Firefox in an existing profile, select it from the list and click Start.

To create a NEW profile for purposes of copying files into it, click the Create Profile button, assign a name like OldSettings, and skip the option to relocate the profile folder. After creating the profile, select it and start Firefox in that profile.

Now you should be back to where you were before.

janiew said

I can't find any of the locations it is referring to and when I create the new profile and the instructions say "leaving that folder open, switch back to Firefox and Exit" I can't get back to the new profile to copy anything in.

You are using the Open Folder button on the Troubleshooting page to launch a new Windows Explorer window showing the files in your currently active Firefox profile. This is the window you want to leave OPEN. To switch to Firefox, you can either click the Troubleshooting page -- assuming it is visible behind the Windows Explorer window -- or you can use the Taskbar to activate that page. Then when you exit out of Firefox, the files in that Windows Explorer window should be unlocked and ready to be cleared out so you can copy the old files into it.

If you are not familiar with using Windows Explorer to view, delete, and copy/paste files, there probably are good articles on that, but I don't think we have any on this site.

Finally got it to work. In Windows 10, it does not like to have 2 file explorer windows open at the same time so switching back and forth is problematic. Thank you for your patience.