Satellite mapping of every building's function in urban China reveals deep built environment disparities.

Decades of rapid urbanization have reshaped China's cities, yet fine-scale built environment disparities remain unclear due to scarce building-level data. Here, we present SinoBF-1, a national building functional map of China that delineates 110 million buildings across 109 major cities using 1-meter multi-modal satellite data. Using nine indicators spanning urbanization intensity, facility accessibility, and infrastructure sufficiency, we quantify disparities across city tiers, geographic regions, and intra-city zones. Analyses reveal that: (1) Across city tiers, accessibility and amenity diversity decline sharply from top- to low-tier cities, while mid tiers show more equitable housing allocation; (2) Geographically, southern cities exhibit the highest access to healthcare, education, and public services but suffer from infrastructure overcrowding; and (3) Within cities, later-expanding zones exhibit greater disparities than early-established urban cores. This study reflects legacies of national development policies over the past half-century and offers a framework for evaluating urban inequality in rapidly urbanizing regions.