Digital platforms are a nearly ubiquitous form of intermediary and infrastructure in society. By positioning platforms in the geographical political economy/ ecology literature, this paper provides a critical analysis of platforms as a dominant form of rentier in contemporary capitalism. In doing so, I extend this work on rent theory beyond applications to land and nature so that it also includes platforms and data. I argue that the rapid rise of the "X-as-a-service" business model across nearly all sectors of the economy is creating rentier relations by another name. This model is premised on the platform latching onto and inserting itself into the production, circulation, or consumption process, thus creating opportunities to capture value. To better understand the operations and implications of platforms, I outline three key mechanisms: data extraction, digital enclosure, and capital convergence.