With these, back up everything, or just what you want,

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

Create a new, blank profile using the Profile Manager.

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

First; open your file browser to the New profile;

Type about:support in the address bar and press enter.

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

Second, open the file browser to the Old profile. You should see it on the directory "tree" in the first file browser. Right click on that folder and select Open In New Window.

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

cookies: Do not bother. Cookies will be created when you return to the web site. However, you will have to log in everywhere.

extensions(add-ons): it would be better to download them fresh. +++++++++++++++++++++++++++++++++++++++++++++++++ key3.db and logins.json: These are the Password files.

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

mimeTypes.rdf: What to do with what type of file.

places.sqlite: History and Bookmarks.

prefs.js: Your settings. Note, this may be contaminated. +++++++++++++++++++++++++++++++++++++++++++++++++ Copy these files from the old to the new. You will get a message about the files already exist. Choose to over-write for each file.

You can backup files like these in the Firefox profile folder.

• bookmarks/history: backups in the bookmarkbackups folder and possibly places.sqlite if you really need the history
• other SQLite files like cookies.sqlite (cookies) and formhistory.sqlite (saved form data)
• logins.json and key3.db (decryption key) for Passwords saved in the Password Manager
• permissions.sqlite and possibly content-prefs.sqlite for Permissions and Site Preferences
• cert8.db for stored intermediate certificates (Certificate Manager)
• sessionstore.js for open tabs and pinned tabs and tab groups

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox