Settings, and addons are all in your profile folder. https://support.mozilla.com/en-US/kb/Profiles Each windows account normally has a separate profile - for privacy and security reasons. You can share the same profile on all 3 windows accounts - but it's not simple. You need to make sure that the shared profile is accessible (read-write) on all 3 accounts. If they're all admin accounts it will be, but if some are limited accounts then you may have to give them read-access. You might choose to use the profile in one user's account for all three - or to set one up in a separate area of disk using the profile manager. You then need to start Firefox with a command-line switch which tells it the location (path) of the profile to use. http://kb.mozillazine.org/Command_line_arguments Make sure that >1 user isn't using the profile at the same time! And be aware of the privacy issue - ''everything'' is shared - cookies, passwords, browsing history, ... !!