The directive itself is kind of involved because it goes pretty deep into what its aim is and eg. what sort of information can be considers an identifier, and it’s actually quite well argued and worth a read if that sort of thing is your, er, thing: eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX… (you need to scoll aaalll the way down to be able to show the body text). I had to deal with this stuff professionally when I was a CTO for a company with some stricter than average privacy requirements due to the field, and I was pleasantly surprised to find out how much sense ePrivacy and GDPR actually make