The Oversight Board, an independent body established by Meta Platforms Inc. to make decisions and recommendations regarding difficult and consequential content moderation questions on Facebook and Instagram, represents a unique experiment in self-regulation of ethical dilemmas in the tech industry. This colloquium will explore the work and experience of the Oversight Board in its first three years of operating, and the challenges that it faces in bringing a sound and effective normative framework to bear on the distinctive difficulties of content moderation at scale.