Sites like Amazon allow you to add items to your shopping cart without requiring you to first log in.
My question is where do they store this data? This data still seems to be there even if you restart the browser too.
This can be demonstrated by how having items in your cart will not transfer between different browsers (which do not share cookies), and also how if you clear your cookies (specifically one they set called session_id), then your basket will be emptied.
The session_id cookie has an expiry date of a long time in the future, so your cart should not be emptied if you close down your browser. If it did, that would be called a
Presumably for a logged-in user, this information is saved instead in their database.