Guidelines 02/2019 on processing of personal data under 6(1)(b) GDPR in the context of the provision of online services to data subjects
Section 3.3 Processing for online behavioural advertising
51. Online behavioural advertising, and associated tracking and profiling of data subjects, is often used to finance online services. WP29 has previously stated its view on such processing, stating:
[contractual necessity] is not a suitable legal ground for building a profile of the user’s tastes and lifestyle choices based on his clickstream on a website and the items purchased. This is because the data controller has not been contracted to carry out profiling, but rather to deliver particular goods and services, for example.