Firefox uses two locations for the Firefox profile folder. *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data One location for your personal data (e.g. bookmarks) and another location for temporary files like the disk cache, so make sure to look in the correct location. Location used for the main profile that keeps your personal data (Root Directory on about:profiles). *C:\Users\&lt;user&gt;\AppData\Roaming\Mozilla\Firefox\Profiles\&lt;profile&gt; ---- You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder. <hr> *bookmarks and history: places.sqlite *favicons: favicons.sqlite *bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder *cookies.sqlite for the Cookies *formhistory.sqlite for saved autocomplete Form Data *logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager<br>key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db *cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager *persdict.dat for words added to the spell checker dictionary *permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences) *sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)