See Something, Say Something Online Act of 2021 This bill requires an interactive computer service (e.g., a social media company) that detects a suspicious transmission to submit a suspicious transmission activity report (STAR) describing the suspicious transmission. A suspicious transmission is any post, message, comment, tag, or other user-generated content or transmission that commits, facilitates, incites, promotes, or otherwise assists the commission of a major crime. Each STAR must be submitted to the Department of Justice and contain (1) the name, location, and other identification information submitted by the user; (2) the date and nature of the user-generated content or transmission detected for suspicious activity; and (3) any relevant text, information, and metadata related to the suspicious transmission. Any provider of an interactive computer service that fails to report a known suspicious transmission shall not be immune from liability for such transmission and may be held liable as a publisher for the related suspicious transmission.