how can facebook find out your under 13?

[Strawberry Flavor]

I was bored so I went on Wikipedia and searched Facebook. Wiki said that Facebook found out that over 5 million kids are under 13 who registered for Facebook. How did they know that those kids were under age? Did their parents tell Facebook or something?

[Lael]

Wiki is wrong a lot of the time but fb probs found out when the kids put in their date of birth.

[Daniel]

Facebook Can Find Out Many Ways People Can Report to Facebook that there Under the Age of 18 Parents Can Also Contact Facebook and let them Know There Are Ways that they Can Find Out

[Steven]

It is not a crime to be on Facebook and be under 13. The only way is for someone to snitch on them. I believe that Facebook would rather keep the under 13 year olds, but has that policy to prevent some sort of legal action, which is unlikely. The more members of any age Facebook has means more advertising money for them.