A Firefox profile stores all of your important data, such as your bookmarks, history, cookies, and passwords. This article explains how to copy files to a new profile, lists important files in the profile and describes what information is stored in these files.

• To sync and share data among multiple profiles and devices, see How do I set up Sync on my computer? and How do I choose what information to sync on Firefox?
• To switch to another profile to recover missing data and settings, see Recover user data missing after Firefox update.

Back up your current profile

Before starting it is recommended that you make a complete backup of your existing Firefox profile in case something goes wrong. Please read the Back up and restore information in Firefox profiles article for instructions.

Create a new Firefox profile

To learn how to create a brand new Firefox profile, please read the Profile Manager - Create, remove or switch Firefox profiles article.

Copying files between profile folders

1. Open the old Firefox profile folder containing the files you want to copy to a new profile.
   If you are copying data from an Old Firefox Data folder created after you refreshed Firefox, simply open the old profile folder it contains; otherwise, if you can open Firefox using the old profile:
   • Click the menu button , click Help and select More Troubleshooting Information.From the Help menu, select More Troubleshooting Information. The Troubleshooting Information tab will open.
   • Under the Application Basics section next to Profile FolderProfile Directory, click Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.Your profile folder will open.
   Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.
2. Close Firefox, if it's open: Click the Firefox menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu and select Quit.
3. Right-clickHold down the Control key while you click on a file you want to copy and choose Copy.
4. Open the new Firefox profile folder as explained in step 1, above.
5. Right-clickHold down the Control key while you click inside the profile folder and choose Paste Item.

Repeat steps 3-5 for each file you wish to transfer over to your new profile folder.

While copying your personal data from an old Firefox profile to a new Firefox profile, it is possible that you could copy over the file that is causing the problem you are trying to get rid of! The more files you copy over, the greater the chance of this happening. It is therefore recommended that:

• You copy over only the minimal amount of files that contain your most important data that you simply can't live without.
• You copy over a few files at a time, and then check that the problem you are trying to get rid of hasn't returned.

Your important data and their files

Bookmarks, Downloads and Browsing History

• places.sqlite

This file contains all your Firefox bookmarks and lists of files you have downloaded and of websites you have previously visited. For more information, see Bookmarks in Firefox.

• favicons.sqlite

This file stores website favicon images. It's best to also include this file when recovering the places.sqlite file.

Passwords

Your passwords are stored in two different files, both of which are required:

• key4.db

This file stores your key database for your passwords. To transfer saved passwords, you must copy this file along with the following file.

• logins.json

Encrypted information about your saved usernames and passwords.

For more information see Password Manager - Remember, delete and edit logins and passwords in Firefox.

Site-specific preferences

• permissions.sqlite

This file stores many of your Firefox permissions that are decided on a per-site basis. For example, it stores which sites are allowed to, or blocked from setting cookies, installing extensions, displaying popups, etc.

Search engines

• search.json.mozlz4

This file stores user-installed search engines. For more information, see Add or remove a search engine in Firefox.

Personal dictionary

• persdict.dat

This file stores any custom words you have added to Firefox's dictionary. If you have never added a custom word to the Firefox dictionary, then you will not have this file. For more information see How do I use the Firefox spell checker?.

Autocomplete history

• formhistory.sqlite

This file remembers what you have searched for in the Firefox search bar and what information you have entered into forms on websites. For more information see Control whether Firefox automatically fills in forms.

Cookies

• cookies.sqlite

Cookies are used by websites for a variety of reasons, some of which include keeping you logged in to a website you have previously logged in to, remembering any preferences a website has allowed you to set, authenticating you as a person who has visited a specific website before, etc.

Security certificate settings

• cert9.db

This file stores all your security certificate settings and any secure website certificates you have imported into Firefox.

File types and download actions

• handlers.json

This file stores your preferences with respect to what Firefox does when it comes across known file types, such as whether you want to save a file or open it with a specific application. For more information, see Manage file types and download actions in Firefox.

Based on information from Transferring data to a new profile - Firefox (mozillaZine KB)