https://www.theverge.com/2019/2/27/18243510/tiktok-age-young-user-videos-ftc-settlement-13-childrens-privacy-law

TikTok will no longer allow children under 13 to upload videos, leave comments, build a profile, or send messages, after a settlement with the Federal Trade Commission today required the company to come into compliance with a federal children’s privacy law.

The changes take effect today for all new and existing TikTok users, who are now being prompted by the app to enter their birthday. Some users have reported that their accounts and videos have been deleted without warning after inputting a birthdate that would make them younger than 13.