This chapter considers what empirical evidence may contribute to the debates around online intermediary liability. What do we need to know in order to frame the liability of intermediaries and, a fortiori, what does the relationship between theory and empirics imply for the wider issue of platform regulation? This chapter evaluates the performance of so-called intermediary liability safe harbours, which have been operating for almost two decades in multiple jurisdictions. The chapter also tackles the problem of transparency of algorithmic decision-making in the ‘black box society’ and how that affects users. In doing so, this chapter reviews the body of empirical studies on copyright intermediary liability during the twenty-year period from 1998 to 2018, drawing on the Copyright Evidence Wiki, an open-access repository of findings related to copyright’s effects. Based on the survey of this body of research, the chapter identifies and discusses five key sub-fields of empirical inquiry pursued so far: the volume of takedown requests; the accuracy of notices; the potential for over-enforcement or abuse; transparency of the takedown process; and the costs of enforcement borne by different parties. Finally, the chapter identifies some of the gaps and limitations in this existing body of scholarship, and offers a number of recommendations for future research.