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Sample configurations:

Note: to delete about:config entries they need to be reset. The next time Mozilla starts, the entry should be gone.

User Agent

general.useragent.override = Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0

More useragent[1] strings:



Want to run multiple Mozilla instances at the same time?

firefox --no-remote -ProfileManager

Profile directory

What are those files in my Profile directory?

Transferring data to a new profile

This is described in detail on, here's the short version:

  • Create a new profile with firefox -ProfileManager
  • Close both the source and the target instance
  • Copy at least the following files to the target profile:
cd ../old.profile
cp bookmarkbackups/bookmarks* ../new.profile/bookmarkbackups/
cp cert8.db cert_override.txt content-prefs.sqlite formhistory.sqlite key3.db \
   permissions.sqlite places.sqlite signons.sqlite ../new.profile/

Now start the new profile, check that everything is in place.


Password Manager

Since Firefox 29, autocomplete=off HTML tags will no longer be honored. Before that, signon.storeWhenAutocompleteOff=true had to be set (and before that signon.overrideAutocomplete=true). This is the default now.



  • global-messages-db.sqlite too big? Try disabling "Global Search and Indexer" under "Advanced" in the Preferences
  • ../Profiles/*/ImapMail/*/*{msf,sbd} too big? Go to Account SettingsSynchronization & Storage and set to Synchronize the most recent XX days instead of Synchronize all.... One has to do this for every account.
  • Reply-All also includes yourself in the recipients list. To disable that, add the exact email address you were addressed with to your "Identities" in your account. You may also have to set mailnews.reply_to_self_check_all_ident to true.
  • Set mail.server.default.send_client_info to false to stop sending the "ID command" to the IMAP server[2], as some may trouble when this command is sent.



After adding the GDATA Provider add-on, the Google calendar can be added via its XML-Link, e.g.


Note: GnuPG is needed!