Copy the profile to a thumb drive.

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.

Warning ! ! Only Copy the files you are told. We will avoid anything that might cause you 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.

I need a way to build a list of all the extensions that were installed. I see an extensions JSON file but I can't read it.

Where does each extension store its setting data? Yes I will download them fresh, but would like to migrate individual setting files where possible.

And what about recovering all the tabs that were open in the previous session?

That is a bit complicated. This add-on can do most of that work for you.

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

sandstorm said

I need a way to build a list of all the extensions that were installed. I see an extensions JSON file but I can't read it. Where does each extension store its setting data? Yes I will download them fresh, but would like to migrate individual setting files where possible. And what about recovering all the tabs that were open in the previous session?

1. - extensions.json can be read in a text editor program, like Notepad or WordPad on Windows. I don't use Win10 so I don't know if those are installed with Win10. In WordPad you can use the Find tool (toolbar button or {Ctrl + F} ) and use "name" the Find parameter. Then jot down the name of each extension as you use "Find Next" to go down thru that file; or if you have many extensions, copy & paste the name into another text file to make list that can be printed or viewed.

2. - Sometimes data or preferences for an extension is stored in the prefs,js file, which can be read in a text editor. Other times data is stored in a .rdf file or in various type files in a separate folder within the Profile folder for some extensions - which would be named for that extension. While other extensions may have their own .json file for data storage. Without a list of your extensions we can't tell you about the specific file or folder names for each extension.

3. - Tabs are stored in a file named sessionstore.js. https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_what-information-is-stored-in-my-profile

You can open a JSON (.json) file in the Scratchpad (Firefox menu button or Tools > Web Developer). Click the "Pretty Print" button to format the file for readability.

You can copy/transfer files like these to your current 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

See also:

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Note that extensions are best be reinstalled to ensure that they are initialized properly.