You are right that you need to copy logins.json and key4.db from the "Old Firefox Data" folder on the desktop to the current profile folder with Firefox closed to recover the logins. Firefox uses two locations in the hidden "AppData" location for the Firefox profile folder. One location in "AppData\Roaming" for personal data like bookmarks and logins and another location in "AppData\Local" for temporary files like the disk cache, so make sure to look in the correct location. Primary 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 use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page (Root directory). *Help -> More Troubleshooting Information -> Profile Folder/Directory:<br>Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data ---- Best is to avoid restoring a full profile folder and only restore important files that are safe to restore/transfer. *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) and key4.db (encryption key/primary password) for logins saved in the Password Manager *cert9.db for 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)