Open source information, particularly digital open source information that is publicly available on the internet, plays an increasingly central role in the landscape of human rights investigations. This article provides a thorough analysis of how open source information is used in practice by UN human rights fact-finding missions, commissions of inquiry and other official human rights investigations. Combining data from semi-structured interviews carried out with investigators with specific experience in open source human rights investigations with a review of reports and other primary and secondary sources, it examines the utility of open source information to UN human rights investigative bodies. It posits that open source research can offer tremendous benefits in planning investigations, supplying lead evidence, and providing direct evidence of violations, thereby overcoming some of the access barriers that investigators face, and potentially giving voice to a wider range of perspectives. On the other hand, this article argues that open source investigations should be approached with a clear eye to their challenges and possible pitfalls. These include the gaps of open source information and the potential to silence already-marginalized communities through open source investigations, as well as the resource-intensive nature of these investigations, the danger that open source information can affect witnesses’ perceptions, and the risks posed by online disinformation. As open source research is likely to comprise an important component of the human rights investigator’s toolbox in the future, this article argues in favour of the institutional buy-in, resourcing, and methodological rigour that it deserves.