‘personal data’ means any information relating to an identified or identifiable natural person (‘data subject’); an identifiable natural person is one who can be identified, directly or indirectly, in particular by reference to an identifier such as a name, an identification number, location data, an online identifier or to one or more factors specific to the physical, physiological, genetic, mental, economic, cultural or social identity of that natural person;
- a hash number falls into this. You cannot just quote recital 26 and stop reading since you found it fitting. Recital 30 covers the case for "other identifiers" that might replace cookies. No hard feelings we all do.
The data might be anonymous for a third party but if you can single out just one person or in other word one unique visitor it is not anonymously. NB. One IP poisons the whole data.
So your fallback is Article 6(f) which is reasonable but you can not assume the interest of a site owner is always higher than the interest of the visitors. You have to put your arguments into writing and have the means for people to appeal it. 6f is not meant as a blanco cheque or batch job...