Cookies are important in CoreMedia because they enable personalization, ad targeting, measurement and analytics, retargeting, and ad control. They allow marketers to deliver personalized experiences, target ads to specific audiences, measure campaign performance, retarget users, and manage ad frequency. However, cookie usage must comply with privacy regulations and user consent requirements.

According to GDPR, no cookie or similar mechanism can be created on a first visit to a website without explicit consent from the visitor. Thus, the most common cookie acceptance campaigns that do not block browsing are only GDPR compliant if no cookies are created until the visitor accepts the cookie policy.

However, different "cookie levels" are defined that differentiate the levels of tracking and data collection. These levels are often defined based on their impact on user privacy and the level of consent required for their use.