The digital computer constitutes a metamedium, hosting all previous media of human communication – speech, writing, printing, cinema, radio, television – while simultaneously supporting new media forms and communicative practices, from the World Wide Web and smartphone apps to the home appliances and traffic systems of an emerging Internet of Things. Digitalization is reemphasizing the point that, more than representations of reality, media afford resources for acting in and on reality as well. This chapter takes stock of research on the ongoing transition to digital infrastructures of human communication and culture, and its implications for the understanding and study of intermediality. The chapter, first, situates metamedia within the long history of human communication, characterizing media as technologies, institutions, as well as discourses. The second section reviews digital media and communication studies since the 1990s, with special reference to the diverse flows of one-to-one, one-to-many, and many-to-many communication on digital platforms. Third, the chapter elaborates on the relationship between metamedia and metacommunication: the many implicit meanings that both anticipate and accompany the transmission or sharing of information. Whereas all human communication is framed and facilitated by metacommunication, the concept has acquired a distinctive and strategic importance in the context of digital media, as their users communicate many-to-one, into the system, leaving behind bit trails with unforeseen, and unforeseeable, applications and abuses. The final section, accordingly, addresses some of the ethical and political implications of metamedia, considering a principle of habeas data to complement the classic principle of habeas corpus.