Dominant social media platforms are increasingly using automation and AI to find and remove problematic content. While this helps stop some of the worst content from spreading on the Internet, algorithmic content moderation can delete content that should not be deleted (overblocking) or discriminate against minorities. Crucially, there is very little transparency from platforms about how algorithmic content moderation works, how accurate its technologies are believed to be, and how much content they remove, especially without human review. As the use of technologies is likely to only increase, regulators should take the initiative on transparency by requiring platforms to make disclosures.