Systems and methods are described for dynamically generating a graphical code that is placed within an advertisement, which may in in turn be placed dynamically over video or image content delivered to a client device. A portion of a stored advertisement unit may be created to have a color-coded section designated to be later replaced with a graphical code. When a user requests to view image or video content on or in which a given advertisement will be shown, a server may generate a tag that contains a URI that includes tracking parameters to identify what advertisement was scanned and/or other data associated with the advertisement, a publisher, or a client device. A graphical code may be generated to represent the given URI, then that graphical code may be inserted into a previously color-coded area of an ad creative before delivery to a client device for presentation.