This study tells the story of how international human rights law emerged as a dominant framework for regulating the exercise of the right to freedom of expression online. Taking as a starting point the emergence of platform law, which elevated social media platforms to the role of new governors of freedom of expression, the study shows how the rise of international human rights law as a central framework for articulating online content moderation issues is the result of the interpretive efforts of actors that international law does not traditionally conceive as primary subjects of the discipline. By examining the practices of UN human rights bodies, corporate entities such as Meta, and independent redress mechanisms such as the Oversight Board, the study illustrates how these actors have become the main drivers for translating the application of human rights law to the exercise of freedom of expression online. In pointing the spotlight to these practices, this study makes two important contributions. First, it demonstrates how the regulation of freedom of expression as exercised online is, today, a site of “entangled legalities”, where platform law is entangled with domestic regimes and international human rights law. Secondly, it reveals how, by taking ownership of the language of human rights, UN human rights bodies, corporate entities, and independent redress mechanisms have become drivers of change in international law. As these developments originated in paths that are beyond traditional mechanisms for change, the study contributes to a better understanding of how international law changes, and of how different actors can be the drivers of legal change.