Examples of the present disclosure describe systems and methods relating to content delivery verification. In an example, a root authority is used to provide aspects of content delivery verification. The root authority receives supplemental content from a content source, which it uses to generate secured content. The content source provides the secured content to a publisher (e.g., directly or indirectly, e.g., via a content marketplace). In examples, the root authority evaluates at least a part of the secured content and/or information associated with the publisher to determine whether the unsecured content should be displayed by the publisher on a client device. In other examples, the client device may perform verification aspects. If it is determined that the content should be displayed, the unsecured content may be provided for display. If, however, it is determined that the content should not be displayed, alternate content may instead be provided.