Firefox lost my profile and I need it back
When Firefox updated in late November 2020 it lost my profile. I copied the contents of the profile folder to a safe location but I need to get the new installation to read it.
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 bar.
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 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.