Urbanization has created transient, ethnically-varied, and densely-populated communities where meaningful human contact is difficult. Urban social norms such as “civil inattention” — a deliberate display of unwillingness to become more familiar with strangers — discourage social interactions among strangers. While these norms help reduce anxiety or fear in overcrowded urban centers they hinder meaningful social interactions in public spaces (coffee shops, museums, and malls, etc.) and events (conferences, galas, etc.) where such interactions should occur. This paper describes CommonTies, a simple technological nudge that managers of interaction spaces and organizers of social events can use to leverage contextual information to encourage social interactions among strangers.