Hi simonwc, sorry to hear about this problem. Were there any major events around the time this occurred such as a Firefox crash, Windows crash, or Windows update?

How much data was affected? Just history, or other data saved in your Firefox such as your bookmarks, any saved passwords, form data, custom preferences, etc.?

Do you see a new folder on your desktop named Old Firefox Data? When Firefox performs a Refresh, your old data is moved into that folder, so if you find one, hang onto it for possible additional recovery options.

Yes everything has gone and I do have an old firefox data file but this appears to be solely the previous old firefox data after an earlier loss. I think firefox had connection issues with my wifi just as it was opening.

Hi simonwc, let me paste something from a few months back. You can skip the first section about Refresh if the contents of your Old Firefox Data is too old.

If you haven't already, you may want to do a normal system shutdown and startup to release any file locks and complete any pending updates.

If your Firefox 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.

It's a lot of things to check, but if you go step by step, it's not too bad.

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 > "?" 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 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, and any session history files they contain.