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Firefox reverted back a few years, need to install my old firefox data

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  • Last reply by cor-el

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After a update my browser was running very slow, I'm not sure what I did but my whole browser, including history and bookmarks and add ons reverted back years. But I have a whole folder of Old Firefox Data which is from today.

How do I get this back on there and get everything back to normal?

After a update my browser was running very slow, I'm not sure what I did but my whole browser, including history and bookmarks and add ons reverted back years. But I have a whole folder of Old Firefox Data which is from today. How do I get this back on there and get everything back to normal?

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You can copy certain files with Firefox closed from one profile folder to another profile folder to transfer your personal data. Best is to avoid restoring a full profile folder and only restore important files that are safe to restore/transfer.

If you decide to transfer extensions and storage, then you need prefs.js to get the extensions UUIDs stored in extensions.webextensions.uuids that link an extension to its storage.


  • 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)

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