The International Criminal Court’s (ICC) Office of the Prosecutor (OTP) has described the preliminary examination as one of its “three core activities,” alongside investigating and prosecuting crimes under the Rome Statute of the International Criminal Court (Rome Statute). Honing in on this once-mysterious “core activity,” this article contributes to the recently expanding literature on preliminary examinations at the ICC by providing a much needed comprehensive picture of all preliminary examinations conducted to date. The twentieth anniversary of the court’s founding treaty, the Rome Statute, provides a timely opportunity for this review as part of the broader effort to take stock of the ICC’s achievements, failures, and future. The article demonstrates that, despite not having full investigatory powers at the preliminary examination stage, the OTP is very active during this phase. It interacts with a wide range of domestic and international actors and makes decisions on important legal issues that go to the heart of the ICC’s work. Paying close attention to preliminary examinations is therefore critical to understanding the OTP’s work, to understanding which actors engage with, and seek to “use,” the ICC, and to understanding important debates about the ICC’s legitimacy.