I'm on Windows 10 v20H2

Hi, did Firefox mention that it was going to do a "tune-up" during the update? That is a Firefox Refresh. It moves your entire old settings folder to your desktop inside that Old Firefox Data folder.

There are two possible approaches:

(1) Selectively copy individual files and folders from the old folder and paste them into the current one (2) Attempt a wholesale transplantation of the old folder and re-educate Firefox as to its existence

For #1, see:

• Recovering important data from an old profile
• Profiles - Where Firefox stores your bookmarks, passwords and other user data

For #2, see the steps I posted in the following thread:

https://support.mozilla.org/en-US/questions/1322197#answer-1384732

Sounds like the refresh feature in Firefox has been used and that a new default profile go created. If that happened in your case then you will have to reinstall all extensions.

when the refresh feature in Firefox is used then a new profile is created and some personal data (bookmarks and history, Form Data, tabs) is automatically imported. The current Firefox profile folder will be moved to an "Old Firefox Data" folder on the desktop. Installed extensions and other customizations (toolbars, prefs) that you have made are lost and need to be redone.

It is possible to recover data from the "Old Firefox Data" folder on the desktop, but be cautious not to copy corrupted files to avoid carrying over problems.

Hi, did Firefox mention that it was going to do a "tune-up" during the update? That is a Firefox Refresh. It moves your entire old settings folder to your desktop inside that Old Firefox Data folder. There are two possible approaches: (1) Selectively copy individual files and folders from the old folder and paste them into the current one (2) Attempt a wholesale transplantation of the old folder and re-educate Firefox as to its existence For #1, see:

• Recovering important data from an old profile
• Profiles - Where Firefox stores your bookmarks, passwords and other user data

For #2, see the steps I posted in the following thread: https://support.mozilla.org/en-US/questions/1322197#answer-1384732

In AppData\Roaming\Mozilla\Firefox\Profiles, there are three profile folders (one from 2019, I don't know why). There's a folder there with the same name as the one in the Old Firefox data.

But when I go to about:profiles, it shows only one profile (with a new name, not the old one).

Can I still try option #2?

Hmm, usually there would not be an identically named folder in both places. Of course, things change, but historically, the Refresh added a long number to the post-Refresh profile (I think it indicates the date/time it was created).

If you want to try with the folder that's in there, skip to step 4 and use the right-hand part of its name as your new profile name.

The have the same folder name in both places but I noticed the one under AppData\Roaming\Mozilla\Firefox\Profiles had only a parent.lock file inside.

Anyway, I copied the folder from desktop (Old Firefox data) into the AppData\Roaming\Mozilla\Firefox\Profiles. During copying, at some point (close to 90% of copying) I got a message of files that cannot be copied due to long path. I clicked skipped, not sure how much this affect things.

Now, I have back the missing parts.

In about:profiles, I have two profiles. Shall I delete the one that lost my data and keep the old one? Or it doesn't really matter since the old one that I reverted is the default?

Thx

I never delete anything myself, but I'm a bit of a hoarder. I'd give it a month to make sure you're not missing anything.