Researchers, policymakers, and competition and regulation authorities worldwide recognise application pro- gramming interfaces (APIs) for powering the digital economy and driving processes of datafication and platformisation. However, it is unclear how APIs tie into the power of, and gov- ernance by, large digital platforms. This article traces the rela- tionality between Facebook’s APIs, platform governance, and data strategy based on an empirical and evolutionary analy- sis. It examines a large corpus of (archived) developer pages and API reference documentation to determine the technicity of platform governance – the technical dimension and dynam- ics of how and what platforms like Facebook seek to govern. It traces how Facebook Platform evolved into a complex layered and interconnected governance arrangement, wherein techni- cal API specifications serve to enforce (changes to) platform policy and (data) strategy. Finally, the article discusses the significance of this technicity in specifying the material condi- tions for app and business development ‘on top of’ platforms and for maintaining infrastructural and evolutive power over their ecosystems.