SAN FRANCISCO, (AFP) - YouTube unveiled a test version of a service that tells people which videos their friends are watching.

YouTube RealTime lets users know when friends are online, what they are viewing and when they comment on or upload videos, according to YouTube product manager Ryan Junee.

In a posting on YouTube's official blog, Junee described RealTime as "a new way of discovering what your friends are doing on YouTube."

Junee said invitations to try out RealTime will be sent to the first 100 volunteers.

"Please keep in mind that you will need to have friends on YouTube for this to work -- the more you have, the richer the experience, so be sure you accept friend invites and actively manage the list," Junee wrote.