57. Joint controllership exists when entities involved in the same processing operation process such data for jointly defined purposes. This will be the case if the entities involved process the data for the same, or common, purposes.
58. In addition, when the entities do not have the same purpose for the processing, joint controllership may also, in light of the CJEU case law, be established when the entities involved pursue purposes which are closely linked or complementary. Such may be the case, for example, when there is a mutual benefitarising from the same processing operation, provided that each of the entities involved participates in the determination of the purposes and means of the relevant processing operation. In Fashion ID, for example, the CJEU clarified that a website operator participates in the determination of the purposes (and means) of the processing by embedding a social plug-in on a website in order to optimize the publicity of its goods by making them more visible on the social network. The CJEU considered that the processing operations at issue were performed in the economic interests of both the website operator and the provider of the social plug-in.
59. Likewise, as noted by the CJEU in Wirtschaftsakademie, the processing of personal data through statistics of visitors to a fanpage is intended to enable Facebook to improve its system of advertising transmitted via its network and to enable the administrator of the fanpage to obtain statistics to manage the promotion of its activity. Each entity in this case pursues its own interest but both parties participate in the determination of the purposes (and means) of the processing of personal data as regards the visitors to the fanpage.
60. In this respect, it is important to highlight that the mere existence of a mutual benefit (for ex. commercial) arising from a processing activity does not give rise to joint controllership. If the entity involved in the processing does not pursue any purpose(s) of its own in relation to the processing activity, but is merely being paid for services rendered, it is acting as a processor rather than as a joint controller.