"With regards to the Children's Online Privacy Protection Rule ("COPPA"), Duolingo only collects personal information from children under the age of 13 for the sole purpose of performing internal operations of the Service."
"When a user creates a Duolingo account we collect their age and compare it to the local standard of child online consent depending on the country they registered in. We refer to users under this age as “child users”."
"Child users are permitted to create a user account but we ask them to provide their parent’s email address instead of their own. We also prevent child users from supplying their own name because we don’t need that information."
