Breadcrumb trails should exclusively feature clickable links to pages that users can actually visit. This navigation tool is designed to reflect the actual structure of the site, guiding users through the different levels they have navigated.

Including any non-navigable categories in breadcrumbs can lead to confusion, as users might expect every element in the breadcrumb trail to be a link to a page they can visit. When these elements turn out to be non-clickable, it creates dead ends in the navigation process, disrupting the user experience.