Not really sure as well but from https://www.gdpreu.org/the-regulation/key-concepts/personal-data/ https://www.gdpreu.org/the-regulation/key-concepts/personal-.

Not really sure as well but from https://www.gdpreu.org/the-regulation/key-concepts/personal-data/ https://www.gdpreu.org/the-regulation/key-concepts/personal-... personal data seems to include "online identifiers", further defines online identifiers as "Natural persons may be associated with online identifiers provided by their devices, applications, tools and protocols, such as internet protocol addresses, cookie identifier"