We examined effects of customizability technology (also known as tailoring or personalization) on political selective exposure and political attitude polarization. Our experiment showed that selective exposure mediated the relationship between customizability technology presence and political attitude polarization. We also found that user-driven customizability (technology that enables users to modify their information environment) weakened the relationship between system-driven customizability (technology that modifies users’ information environment unobtrusively, without active involvement of the users) and political selective exposure. This research contributes to a better understanding of how important characteristics of today’s communication environment influence political selective exposure and political attitude polarization.