https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

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

Type about:profiles<enter> in the address box. How many profiles are listed? How many should be there? Also, open the profile folder in your file explorer.

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Hello Fred, Just received your message; thanks for the help. Here are the facts in response to your articles and questions: - I'm using Mac 10.13.6; most articles listed use Windows as examples so usefulness is limited. - Your Q.1: There are currently five profiles listed in the Profile Manager (about:profiles), all of which have been created by the recent upgrade to 99.0.1. None of them have any my original data. All are useless. - Your Q.2: This is interesting. In an effort to get back some of my former data, I downloaded yesterday the three most recent FF profiles from TimeMachine backup. They didn't appear right away but today they are in the Profile folder (Library/ApSupport/FF/Profile). That folder now has three older profiles from backup that I believe are good and one of the newest, indeed the one that the new version of FF is using as default. Those are the only four in that folder. - There are two items in the Library/FF folder, one step up from the Profile folder, that may not have been there before; I'm not sure. One is called "installs.ini" and the other is called "profiles.ini". I don't know their purpose or relevance to this problem. - My inclination now is to erase the recent upgraded version of FF from the Mac and perhaps the Profiles Folder as well; everything may be corrupted and it's better to rebuild from backup with an older yet working version and stick with that. I've used FF since its early days so all my bookmarks and other data is tied up with it. Accordingly, these past few days have been a painful waste of time and worry. I'll wait on that acton and look forward to your additional questions and suggestions. Again, many thanks. Ron ps: I'm in San Francisco. If a phone call can help send me a number or I'll send mine.

Once you have found a working profile, be sure to back it up just in case.

Back up and restore information in Firefox profiles {web link} I use a Legacy add-on that makes backups of my user profile, Just In Case. Unfortunately, it is not compatible with the current Firefox.

Every now and then, open the profile folder and create a copy of the current profile as is to another location on your hard drive. This way you will have a backup.

If you do this each day, you will not lose much data. This should be done with Firefox Closed.

Note: In case you need to restore from these backups, you may need to overwrite old or corrupted files.

Hello Fred,

The question buried in my last message is this: How to use any one of the three Profiles that I have brought from backup (therefore they each should work) and put into the Firefox Profile folder in the Library section of my Mac?

The new version of Firefox does not "see" or use that folder. It creates its own new profiles and presumably stores them someplace but I don't know where. How do I delete all the useless profiles and have the application only see/use the three that I know are good?

There has been nothing simple or intuitive about this problem that has stopped much of my work for nearly a week.

What are the specific steps to use on a Mac to clear out the useless profiles, and have the application only use the uploaded-from-backup profiles?

Please help.

Thank you.

Pick one of the current profiles that work.

I take it the new profile is working without a problem, yes?

When you are ready, we can start moving parts of your old data and Copy it to the new profile.

First; open your file browser to the New profile;

Type about:support<enter> in the address box.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show/Open Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Second, open another file browser to the Old profile.

Warning ! ! Only Copy the files you are told. We will avoid anything that might cause problems. Here is the list of files;

cookies: cookies.sqlite Do not bother. Cookies will be created when you return to the website. However, you will have to log in everywhere. And you may lose any settings that websites store on your computer.

extensions(add-ons, themes): it would be better to download them fresh. If you need to remember what add-ons you had, open the extensions sub-folder and look at the .xpi files

logins.json and key3.db [v58+]key4.db : These are the password files. Copy Both !

persdict.dat : custom dictionary - words you added to the dictionary

mimeTypes.rdf [v55+]handlers.json : What to do with what type of file.

places.sqlite : History and Bookmarks.

prefs.js : Your settings. Note: If you were having problems, this could be contaminated.

cert8.db [v58+]cert9.db and possibly cert_override.txt : Stores all your security certificate settings and any SSL certificates you have imported into Firefox. If removed, the cert8.db, cert9.db file will be replaced.

search.json.mozlz4 : file stores the user-installed search engines that are available in the Firefox v47+

search.sqlite file and searchplugins folder store the search engines that are available in the Firefox Search bar before Firefox v47

Copy these files from the old to the new. You may get a message that the files already exist. Choose to over-write for each file.