Today, the centrality of cities in the global sustainability challenge is widely acknowledged, and numerous initiatives have been developed worldwide for monitoring and comparing the sustainability performance of urban areas. However, the escalating abundance of indicators makes it difficult to understand what really counts in urban sustainability and how to properly select the most suitable indicators. By methodically collecting and mapping the diversity of available indicators, our work aims to elucidate the emphases, as well as the gaps, that exist in the way urban sustainability is currently translated into metrics, and to draw instructive lessons to support the development of future indicator sets. Representing the most comprehensive study ever performed in the field, this analysis relies on both an innovative research approach entailing multi- and cross-typological systematic analysis of indicators and an extensive data sample comprising 67 indicator sets (for a total of 2847 indicators) from academia and practice. The findings highlight the most frequent indicators in urban sustainability measurement initiatives, and demonstrate the prominence of social issues (e.g., quality of life, access to services, consumer behaviour, employment) and to a lesser extent, of environmental stakes. In contrast, urban sustainability indicator sets generally pay marginal attention to political questions (e.g., participation, policies, institutional settings), gender issues and distributional concerns. From a systemic point of view, the analysis reveals the strong emphasis placed on the status of actual and potential resources as well as the satisfaction of current needs. The study further highlights seven key lessons on how to deal with three typical tensions faced during indicator selection processes: (i) parsimony vs. comprehensiveness; (ii) context-specificity vs. general comparability; and (iii) complexity vs. simplicity. The directly implementable recommendations proposed herein will support both scholars and practitioners in the design of future urban sustainability measurement initiatives.