The data controller
The data controller has the greatest duty under GDPR and other privacy regulations for preserving the privacy and rights of the data subject, such as a website user. Simply expressed, the data controller is in charge of data utilization methods and objectives.
In brief, the data controller is responsible for dictating how and why the business will utilize data.
A data controller may use its own methods to process gathered data. In some circumstances, however, a data controller must collaborate with a third party or external service in order to process the collected data.
The data controller will not cede custody of the data to the third-party provider, even in this circumstance. The data controller will maintain authority by dictating how the data will be used and processed by the external service.