Note that you should always disconnect a profile from Sync before removing it or modify/remove data that is part of Sync. Best is always to backup your personal data locally to be sure you lose nothing if you aren't sure.

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

You can check compatibility.ini in a profile to see what Firefox version last used the profile. You can also check the last modified date/time of files in the profile folder.

Thank you for your reply. All of this is new to me. I do not understand the relationships of profiles, versions, devices, and synching. Can you recommend a tutorial?

Hi Bill, in short, Firefox stores your browsing data and settings in a profile folder. You can create multiple profiles (profile folders) if you need separate data and settings, for example, for home and work.

Signing Firefox into a Mozilla/Firefox Account provides access to Sync, a service to synchronize settings and some browser data between different Firefox installations. It can also synchronize data deletions among Firefox profiles on the same computer.

As a starting point, could you open the about:profiles page: type or paste about:profiles in the address bar and press Enter to load the list. These are the profiles Firefox is aware of (meaning, the profiles listed in a configuration file). Possibly you will only find the newer pair of folders, or you might see all four.

Take a quick glance at the page and make a mental note of which Profile has this notation: This is the profile in use and it cannot be deleted. That is your current default profile and one you would NOT want to delete.

The page provides Remove buttons for other profiles, and if you are wondering what is stored in that profile, you can click its Launch profile in new browser button to load those settings/data into a new window. Do not connect that profile to your Mozilla/Firefox Account if it wasn't connected before. When you are done checking that, you can close the extra window without affecting your regular Firefox profile.

Any progress so far?

Thank you. Following your directions, I deleted the older of my two profiles with Profile Manager. I don't like to have unnecessary clutter! I guess my original question, about loss of passwords and other data, is moot.

The two folders that are not even listed on about:profiles can probably be deleted as well, but if you are curious about how to investigate them further, there are some ways to do that.

Yes, I'm interested...

Firefox uses two locations in the hidden "AppData" location for the Firefox profile folder. One location in "AppData\Roaming" for personal data like bookmarks and logins and another location in "AppData\Local" for temporary files like the disk cache.

Primary location used for the main profile that keeps your personal data (Root Directory on about:profiles).

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>

Secondary location used for the disk cache and other temporary files (Local Directory on about:profiles).

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>

To examine what is in "06m8lkgu.default-release, 9/21/2023" you can educate Firefox about it by adding it as a new profile. Here's how:

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

• Click the "Create a New Profile" button, then click Next.
• Assign a temporary profile name like test-old and Firefox should show a proposed folder name with a new random part.
• Click the "Choose Folder..." button and select the "06m8lkgu.default-release" folder (not your regular default-release folder) so that Firefox picks up the full old name.
• Back in Firefox, click the Done button.

After creating a new profile, Firefox usually makes it your default profile (for external links and the next startup). To avoid a rude surprise at your next startup, find your regular "default-release" profile and click the Set as Default Profile button below that profile.

And then, finally, scroll down to "test-old" and click the Launch profile in new browser button.

Anything interesting in there that you want to save?

The "local" path leads to 2 folders:

    06m8lkgu.default-release, modified 9/21/2023, 12.2 Mb
    lamrm8zp.default-release, modified 2/27/2024, 1.02 Gb

The "roaming" path leads to 3 folders:

   06m8lkgu.default-release, modified 9/21/2023, 65 Mb
   lamrm8zp.default-release, modified 2/27/2024, 370 Mb
   x0wvrqsi.default, modified 5/4/2022, 47 Bytes

default-release is my default (and only) profile

Which of these (if any) do you think I can delete? With respect, your statement that there are folders that can "PROBABLY" be deleted, makes me wary.

It looks that x0wvrqsi.default is empty with only one times.json file, could a failed or canceled profile creation.

This is your current profile according to the modified date and id probably the one you see in about:profiles, so you shouldn't remove this one.

• lamrm8zp.default-release

You can check compatibility.ini in the other 06m8lkgu.default-release profile to see what Firefox version last used the profile. You may want to keep some files in this profile as a backup.

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins) and key4.db (encryption key/primary password) for logins saved in the Password Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Thanks. I think I'll just leave everything alone.