I do not store my usernames and passwords in firefox, I use a password manager. I also disable Remember Passwords and "Remember search and form history" For some reason before I unlock my password manager my "user name" from Site A is inputted into Site B's login field... How? It should have never been saved by anything in the browser yet it exist somewhere. I made two alterations in about:config browser.formfill.enable false browser.formfill.expire_days 1 This stopped it from inserting the username and I'm hoping this will remove the username from wherever it's saved but I want to know what file it was that contains form information?