What step must be taken before initiating a fullscreen expansion?

Before any rich media creative functionality, including fullscreen expansion, can be used, the Enabler must be initialized. The Enabler is a JavaScript library that facilitates communication between the creative and the ad server, providing essential functions like tracking, dynamic content, and ad serving events. Without proper initialization, these functions, including the fullscreen API, will not be available or will not work correctly, leading to errors or unexpected behavior. Establishing a connection to a dynamic feed is only necessary if the creative uses dynamic content, not for fullscreen expansion itself. Adding a polite loader is a best practice for user experience, ensuring content loads smoothly, but it's not a prerequisite for the technical functionality of fullscreen expansion. Determining the screen size is often done within the creative's logic to adapt layouts, but it's not a prerequisite for initiating the fullscreen API call; the Enabler's initialization is.