Investigating the structural transformation of the public sphere should reckon with the secret and its modes of organization. The expansion of secrecy effected by the infrastructures, platforms, and applications of media technology is constitutive for the emergence and transformation of ‘digital publics’. Offering a rereading of Habermas’s Structural Transformation of the Public Sphere that is attuned to the organizational principle of secrecy, this paper discusses current notions of mediated publics in juxtaposition with the redoubling of media-technological and organizational secrecy at work in platform society. How are illegibility, opacity and unavailability organized? Instead of assuming accountability, publicity and transparency as epistemological a priori, investigating the transformation of the public sphere would benefit from adopting epistemes of secrecy and opacity.