Every country whose address you look up here gets a stamp. The passport is kept in this browser only — no account, and we never see the list.
Open any address page, a country index or the duel and the country that address belongs to is stamped on the passport, once per country. The address you are connecting from is kept separately, as your "home" stamp, so it is easy to see which countries you have browsed and which one is actually yours.
A stamp list is a record of what you looked at. Keeping it on the server would mean storing a personal browsing trail, which is exactly what our privacy policy says we do not do. In your browser the list is yours: clear it and it is gone, and it never leaves the device unless you export it or share the line below.