Despite the widespread suggestion that decreases in psychological well-being among youth since 2010 are partly due to increases in distressing social comparisons with idealized portrayals of others on social media, this registered report is the first empirical test of whether social comparisons actually have changed since the advent of social media. Using event-contingent experience sampling, undergraduate participants from two comparable cohorts 27 years apart (N = 232participants in 1997–1998 and 234 participants in 2024–2025) each described 10 naturalistic social comparisons (4,660 comparisons total). The results revealed sizable cohort effects: Compared to their 1990s counterparts, students in the 2020s were more prone to compare automatically, compare with distant rather than close others, compare upward with others’ desirable attributes, and feel worse about themselves while making comparisons. The 2020s cohort also reported generally lower selfesteem and higher levels of depression. Examining the contexts in which the 2020s cohort made social comparisons revealed that comparisons made while using social media were more liable to be upward comparisons with distant targets that left people feeling insecure and disconnected. Collectively, these results suggest that social media comparisons could be one driver of the observed generational shifts in everyday social comparison experiences and psychological well-being.