Clean Slate for Kids Online Act of 2021 This bill allows individuals over age 13 (or their guardians, if applicable) to request the deletion of information collected from or about them while they were under age 13 by a website or online service that is directed to children. Specifically, the bill requires an operator of such a website or service to provide notice on their website about how an individual over age 13 (or the guardian of an individual over age 13) can request the deletion of all personal information in the operator's possession collected when the individual was under age 13; promptly delete, upon request, all such personal information; and provide written confirmation of deletion. The bill allows a limited exception to the deletion requirement if the personal information collected from or about a child is necessary to (1) respond to a judicial process, or (2) to provide information to law enforcement agencies or for an investigation related to public safety.