Social media platforms structure the ways in which billions of citizens access information. Nevertheless, to assess social media time use, most research relies on limited data sources, such as self-reported survey measures or behavioral data from single platforms or convenience samples. Using 6 weeks of passive metering of smartphone and computer activity from a quota sample of Italian adults (18â70, n = 1,457), this study provides a behaviorally measured account of platform-specific social media use across the adult population. We quantify time allocation across Facebook, Instagram, TikTok, YouTube, and Twitter/X and examine how use varies by sociodemographic factors. Results show that Facebook and YouTube dominate everyday social media time, accounting for nearly three-quarters of consumption, while Instagram attracts comparable average time from a narrower user base, and TikTok shows concentrated usage among younger adopters. Twitter/X occupies a marginal niche. Use is overwhelmingly app-based (>90%), a pattern that browser-based measurement cannot capture. Age is the strongest demographic predictor: Gen Z concentrates attention on Instagram and TikTok, while older cohorts favor Facebook; YouTube shows weak demographic patterning. Gender and education are consistent secondary predictors: women devote more time to Facebook, Instagram, and social media overall, and higher education is associated with lower aggregate use and a smaller share on Facebook and TikTok. Employment and income show null effects. Together, these behavioral, cross-platform figures provide a more accurate basis for weighting platforms by their actual audiences than self-reported or single-platform evidence allows.