Internet and social media platforms face growing challenges in moderating the content posted by users, deploying a range of policies to find, flag, and remove offensive or inappropriate material. This study will combine computer science and law approaches to conduct an empirical study of the moderation policies and practices of platforms such as Youtube, Reddit, Facebook, and Etsy, creating the first public corpus of these policies and auditing how these systems are applied in real situations. The researchers will also conduct surveys and interviews to assess how users of these platforms perceive these policies and their expectations for how content rules will be enforced.