Researchers, policymakers, and competition and regulation authorities worldwide recognize the utility of application programming interfaces (APIs) in powering the digital economy and driving datafication and platformization processes. However, it remains unclear how the APIs of leading social media relate to platform governance and how this relationship evolved. This article traces the evolution of Facebook’s APIs, which evolved from a relatively simple programming interface for data access into a complex layered and interconnected governance arrangement. The study draws on a large corpus of (archived) developer pages and API reference documentation to examine the history of Facebook’s API governance; that is, the governance of and by Facebook through its APIs. This historical analysis emphasizes the technical dimensions and dynamics of what, how, and whom powerful platforms seek to govern, thus highlighting the technicity of platform governance and how it evolved. Because APIs facilitate and govern the material conditions of app development and the social and economic processes they sustain, powerful platforms influence the evolution of their larger ecosystems. As such, the technicity of Facebook’s API governance represents a major source of the platform’s “infrastructural power.”