  Cookie banners are devices implemented by websites to allow users to manage
their privacy settings with respect to the use of cookies. They are part of a
user's daily web browsing experience since legislation in Europe requires
websites to show such notices. In this paper, we carry out a large-scale study
of more than 17,000 websites including more than 7,500 cookie banners in Greece
and the UK to determine compliance and tracking transparency levels. Our
analysis shows that although more than 60% of websites store third-party
cookies in both countries, only less than 50% show a cookie notice and hence a
substantial proportion do not comply with the law even at the very basic level.
We find only a small proportion of the surveyed websites providing a direct
opt-out option, with an overwhelming majority either nudging users towards
privacy-intrusive choices or making cookie rejection much harder than consent.
Our results differ significantly in some cases from previous smaller-scale
studies and hence underline the importance of large-scale studies for a better
understanding of the big picture in cookie practices.
