The First Amendment restricts government, not private companies. But a handful of private platforms now host much of public discourse, raising the question of whether traditional speech principles are adequate to that arrangement.
Section 230 of the Communications Decency Act shields online services from liability for user-posted content and protects their ability to moderate. It is central to nearly every proposal in this area, and is frequently described inaccurately in public debate.
Platforms moderate for many reasons: legal compliance, advertiser requirements, user experience, and stated policy. Scale means most decisions are made by automated systems, which produce both false positives and false negatives at volume.
Government pressure on platforms to remove content raises distinct constitutional questions, since informal pressure on a private intermediary can produce outcomes the state could not impose directly.