Firefox normally stores your personal data like bookmarks, saved passwords, history, etc., in a personal profile folder in your Windows User folder. When you log in as a different Windows user, Firefox is going to check ''that'' User folder for your stuff. The optional Firefox account would be for ''that'' Firefox profile (or a Sync account shared between profiles/devices). Do you want to share a single profile folder? If so, I'm not sure of the best way to bypass the normal Windows permission design, but I'm sure that people have posted ways to do it over the years. Somewhere! If you only want to share some data, you could use Sync to copy bookmarks and other selected data between the two profiles. I don't use Sync myself, but we have several articles on it: [[How do I set up Sync on my computer?]] '''Please make backups before experimenting.''' This article has suggestions for that part: [[Back up and restore information in Firefox profiles]].