This was located in their terms of service. However, in 2009 it was removed and relocated to Twitter’s privacy policy, which now states:
Twitter doesn’t ask your age when you sign up, but Facebook does, and on Facebook the minimum age requirement is a hard and fast 13. It’s the same number on Instagram, Pinterest, Tumblr, Reddit, Snapchat and Secret, too.
Check the visual below for more social media minimum age requirements, which comes courtesy of Linneyville.
(Source: Linneyville. Social media apps image via Shutterstock.)