Google+ is now open for the over-13s to join, bringing the social network in line with rivals Facebook and MySpace.
And, it says, it's introducing new safety requirenments for this age group, with controls on who can contact teens and restrictions on group video chat.
"In life, for instance, teens can share the right things with just the right people (like classmates, parents or close ties). Over time, the nuance and richness of selective sharing even promotes authenticity and accountability," says Bradley Horowitz, Google+ product vice president, on the company blog.
"Sadly, today’s most popular online tools are rigid and brittle by comparison, so teens end up over-sharing with all of their so-called 'friends'."
Default settings for the under-18s will be tighter than those for adults, and changing settings will trigger warnings.
For example, when teens post something to an extended circle or to the public, they'll receive a warning reminding them that the content will be public. And the default setting for 'who can notify me' will be people in teens' circles, rather than everyone, as with adults.
Only people within teens' circles will be able to comment on their posts or see a teen's relationship status. Profile features such as contact information and birthdate will be set to 'only me', and location information won't be provided with posts.
When a teen's in a Hangout video chat and someone outside their circles joins in, the teen will be pulled out for a moment and asked to confirm that they want to continue.
"Our approach is straightforward: build awesome features that teens really want, encourage safe behavior through appropriate defaults and in-product help, and make abuse reporting tools easy to find and use," says Horowitz.
The move won't apply in Spain, South Korea and the Netherlands, where national age requirements are higher.