<p>Urban areas account for a large and growing share of global carbon emissions, yet the role of urban form in shaping these emissions remains insufficiently understood. While existing studies have primarily focused on urbanization rates or population density, less attention has been devoted to the geometric configuration of cities and its relationship with sector-specific emissions over time. In this paper, we examine the association between urban compactness and carbon emissions using a global panel of more than 11,000 urban centres over the period 1975–2020. We combine harmonized definitions of urban areas with high-resolution data on residential and on-road transport emissions and multiple geometric indicators of urban form. We find that more compact urban configurations are associated with lower per capita emissions in both sectors. However, the strength of this relationship varies substantially across regions, being stronger and more robust in low- and middle-income countries, and weaker or not statistically significant in high-income regions. These results are robust across alternative specifications but should be interpreted as conditional associations rather than causal effects. Overall, the findings highlight the relevance of urban form as a dimension of environmental performance, while underscoring the importance of economic and institutional context.</p>