Social media recommender systems play a central role in determining what content is seen online, and what remains hidden. As a point of control for media governance, they are subject to intense controversy and, increasingly, regulation by European policymakers. A recurring theme in such efforts is transparency, but this is an ambiguous concept that can be implemented in various ways depending on the types of accountability one envisages. This paper maps and critiques the various efforts at regulating social media recommendation transparency in Europe, and the types of accountability they pursue. This paper identifies three different categories of disclosure rules in recent policymaking: (1) userfacing disclaimers, (2) government auditing and (3) data-sharing partnerships with academia and civil society. Despite their limitations and pitfalls, it is argued, each of these approaches has a potential added value for media governance as part of a tiered, variegated landscape of transparency rules. However, an important element is missing: public disclosures. Given the deeply political and value-laden context of media governance, it is argued, this field cannot rely exclusively on technocratic, institutionalized forms of transparency emphasized in current proposals. The final section articulates the distinct benefits of public disclosures as a supplement to existing transparency measures, and suggests starting points for their design and regulation.