Since the 1990s, friction has pervaded Silicon Valley discourses as a metaphor for obstacles to the flow of capital, and its eradication has become a mission statement of platform capitalists. However, despite their aspirations of endless growth, friction persists because the process of platformization, through which platforms scale, is never seamless. In this introduction to a Special Issue on friction and platform capitalism, we locate friction in the encounter between the standardizing, scaling forces of platformization-and by extension platform capitalism-and the diverse and often stubborn localities in which platformization becomes instantiated. Friction is not resistance to platform power; it is the site where platform power and the contours of platformization are negotiated. We trace platform frictions across three contexts: policy, design and labor, and market relations. We argue, aided by the contributions to the Special Issue, that examining platform frictions reveals the contingencies of platform power and actually existing platformization, frustrating their claims of universality and inevitability.