To set up Dynamic Remarketing, what must first be created in Google Analytics?

To set up Dynamic Remarketing in Google Analytics, it is essential to create a Custom Dimension. This allows you to define and attach additional information about your users' activities and interests. Dynamic Remarketing specifically relies on user-specific data pulled from your website or app, such as the products viewed or purchased, to serve personalized ads to users as they browse other sites in the Google Display Network.

Custom Dimensions enable you to capture unique attributes related to your users or their interactions. By configuring these dimensions to track specific identifiers, such as product categories or user interests, you ensure that the remarketing system can effectively tailor advertisements based on user behavior. This personalization is crucial for the success of Dynamic Remarketing campaigns, as it increases relevance to the user, improving the likelihood of engaging them again.

Other options, such as custom segments, custom metrics, or custom reports, do not provide the necessary framework for creating the personalized user data needed for Dynamic Remarketing. Segments are used for analyzing subsets of data, metrics are quantitative measurements, and reports are meant for visualizing and sharing data insights, but none of these directly facilitate the setup for tailored advertising campaigns dependent on user behavior like Custom Dimensions do.