<p>Urban areas are significant contributors to global CO₂ emissions, necessitating robust monitoring networks to accurately quantify and mitigate emissions. Atmospheric in situ observations provide high-precision data, enabling multi-year tracking of urban emission reduction trends. However, significant geographical disparities exist, with well-established networks in Western Europe, North America, and East Asia, while regions like Eastern Europe, South America, South Asia and Africa remain critically underserved. This review evaluates advanced global methodologies, informed by insights from ten long-term urban monitoring networks and research across more than 20 cities, focusing on urban background determination and the design of spatially resolved, city-scale monitoring networks, while assessing the impact of biogenic CO₂ fluxes on monitoring accuracy. We highlight China's rapid advancements in urban carbon monitoring and address ongoing challenges, such as the spatial separation of urban cores and industrial emission zones due to industrial relocation, and the blurred boundaries of carbon emissions in expanding urban agglomerations. Emphasizing the importance of customizing network designs to specific city types, the review integrates long-term global projects and emerging techniques to strengthen urban CO₂ monitoring frameworks. Challenges include expanding global urban network coverage, integrating top-down atmospheric measurement with bottom-up inventories, optimizing networks for diverse urban environments, and reducing uncertainties caused by meteorological and biogenic factors. Drawing on global best practices, we emphasize the importance of international collaboration, technology transfer, and data-sharing mechanisms. Tailored strategies are proposed to enhance and expand urban monitoring networks, which are essential for improving emission estimates, informing climate policies, and advancing global carbon neutrality goals.</p> Graphical Abstract <p></p>