Openness has a long genealogy in education. Whether through the use of post, radio, television and digital technologies, extending learning opportunities to more and a wider range of people has been a significant aspect of educational history. Transcending barriers to learning has been promoted as the means of opening educational opportunities in highly normative ways, focusing on the media through which to remove the limits of institutional selection, and of space and time. While there is an obvious attractiveness is such notions, they do little to engage with the critical research on the selectiveness and exclusions inherent in all curricula and pedagogic approaches, however open. The nature, scale and range of digital technologies have seen resurgent interest in the possibilities of openness in education. However, these technologies work on the basis of ontologies, code, algorithms and standards to build knowledge infrastructures that are not always open or opening. This article will suggest that the work of the knowledge infrastructures of open education results in an inherent inscrutability within its practices, which is elusive in terms of significance, processes and effects.