The Children's Online Privacy Protection Act of 1998 (COPPA) is a United States federal law, located at 15 U.S.C. §§ 6501–6506 (Pub.L. 105–277 (text) (pdf), 112 Stat. 2681-728, enacted October 21, 1998).
The act, effective April 21, 2000, applies to the online collection of personal information by persons or entities under U.S. jurisdiction about children under 13 years of age including children outside the U.S., if the company is U.S.-based.
Although children under 13 can legally give out personal information with their parents' permission, many websites—particularly social media sites, but also other sites that collect most personal info—disallow children under 13 from using their services altogether due to the cost and work involved in complying with the law.