We introduce a novel measure of segregation, experienced isolation, that captures individuals’ exposure to diverse others in the places they visit over the course of their days. Using novel Global Positioning System (GPS) data collected from smartphones, we measure experienced isolation by race. We find that the isolation individuals experience is substantially lower than standard residential isolation measures would suggest. Experienced and residential isolation measures are highly correlated across metropolitan areas. Individuals are more racially isolated close to home, and are less isolated in public spaces like parks, retail establishments, and restaurants. The gap between residential isolation and experienced isolation is larger for Blacks than for Whites.