Curtain Call is a free Chrome extension designed to prevent unwanted fullscreen popups that can disrupt browsing experiences. It effectively blocks any fullscreen requests from websites that are not on the user's allowed list, ensuring a smoother and more controlled web environment. Users can add specific sites to the allowed list, providing flexibility in managing which websites can initiate fullscreen mode.

This tool is particularly useful for those who frequently encounter intrusive alerts and popups, such as "Critical Alert, call this number" messages that take over the browser. By utilizing Curtain Call, users can significantly reduce the annoyance of fullscreen hijackers and maintain better focus while browsing online.