This disclosure relates to systems and methods for expanding a social network. A method includes retrieving contact lists from a plurality of devices, generating a list of associations between identifiers in a first communication channel and identifiers in a second communication channel, removing, from the list of associations, one or more associations that include identifiers that do not represent contacts that are not members of the online social networking service, and transmitting an invitation to join the online social networking service to the second identifiers on the second communication channel for associations that remain in the list of associations.