A default banner is a pre-set image or graphic that appears as the header or top section of a website, social media page, or online platform. It is typically used when no custom banner has been uploaded or selected by the user, and serves as a placeholder until a personalized banner is added. Default banners often feature generic designs or branding elements of the platform, and can be changed or removed by the user at any time. They provide a visual representation of the page or site and can help to establish a cohesive aesthetic for the overall design.