Milady

https://takeout.google.com/

You can, on firefox at least. No add ons required it’s a browser feature.

Cookies fall short just the same as sessions. you’re asking the user to pinkie promise they won’t clear their cookies / modify them.

An account seems the most logical. You need to avoid duplicates ; it’s not really about privacy here. You’ll only make a tradeoff between accomplishing no duplicates and letting users do what they want.

Cookies are really inappropriate for this use…