Thanks and happy new year
do you have analytics running on your site? jekyll on its own is not setting a cookie.
what is the name of the cookie?
Ok I found the culprit via the cookie name. It was an autodeletecachecookies cookie by an addon of firefox namly cookie auto delete…kinda awkward that an addon to delete cookies needs to set one prior:D.
So this is solved. thanks for the hint @rdyar =)