An essential argument of the social diversification hypothesis is that disadvantaged groups use the Internet rather than face-to-face communication to broaden social networks, whereas advantaged groups use the Internet to reinforce existing network ties. Previous research in this area has not accounted for both online and off-line communication, has only been examined with cross-sectional data, and has primarily been studied in Israel. To address these gaps with a U.S. data set, 2,669 conversations were analyzed over 6-day periods using ecological momentary assessment (EMA). Indeed, unlike participants from racially or educationally advantaged groups, participants who were from a racially marginalized group or lacked college training were more likely to broaden social networks online rather than face-to-face with interracial and weak tie exchanges. This proof of concept of social diversification theory across cultures is the first to use real-time, within-person measures of both race and tie strength.