| File | File type | Definition | More details |
|---|---|---|---|
| places.sqlite | Bookmarks, downloads, and browsing history | It contains all your Firefox bookmarks and lists of files you have downloaded and of websites you have previously visited. | Bookmarks in Firefox |
| favicons.sqlite | Bookmarks, downloads, and browsing history | It stores website favicon images. Use it when recovering the places.sqlite file. | Bookmarks in Firefox |
| key4.db | Passwords | It stores your key database for your passwords. To transfer saved passwords, you must copy this file along with the following file. | Password Manager - Remember, delete and edit logins and passwords in Firefox |
| logins.json | Passwords | Encrypted information about your saved usernames and passwords. | Password Manager - Remember, delete and edit logins and passwords in Firefox |
| persdict.dat | Personal dictionary | It 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. | How do I use the Firefox spell checker? |
| formhistory.sqlite | Autocomplete history | It remembers what you have searched for in the Firefox search bar and what information you have entered into forms on websites. | Control whether Firefox automatically fills in forms |
| cookies.sqlite | Cookies | 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. | Cookies - Information that websites store on your computer |
The above list includes only essential files you may wish to copy to a new Firefox profile. See Restore bookmarks, passwords and data from an old Firefox profile for details on how to transfer this data.
Profile data that may cause problems if transferred, such as user preferences or Firefox extensions, are not listed. To learn more about other data stored in your Firefox profile, see Profiles - Where Firefox stores your bookmarks, passwords and other user data.
Based on information from Transferring data to a new profile - Firefox (mozillaZine KB)