822 ITU‐T's Technical Reports and Specifications 1 Introduction Within the context of an increasingly interconnected society, information and communication technologies (ICTs) are playing a role as part of novel approaches to address urban challenges. They are an intrinsic component of smart sustainable cities (SSC), contributing to the improvement of citizens' quality of life, the provision of public services, and the achievement of sustainable development goals, among others. Both established as well as emerging ICTs, including mobile broadband, Internet of things, cloud computing, big data, and next‐generation networks (NGNs), have been involved in the establishment of smart sustainable city strategies. Many of these tools are being deployed globally, giving momentum to the next revolution of technology and industry that combine intelligent and sustainable features. However, as the design and implementation of SSC strategies continues to unfold, it becomes vital to develop robust indicators that allow to monitor, measure, and better understand both the technical requirements, as well as the social and environmental implications of ICTs use in urban settings. In order to further enhance the understanding of how ICT solutions can make cities smarter and more sustainable, as well as to support decision‐makers, practitioners and citizens alike in the development of novel approaches to urban development, ITU‐T Focus Group on Smart Sustainable Cities (FG‐SSC) is developing a set of key performance indicators (KPIs) to measure and assess ICT's impact on SSC. 1.1 Scope The purpose of this Technical Report is to serve as a supplement to the content presented in the series of KPIs Technical Reports (TRs) and Technical Specifications (TSs) developed by FG‐SSC, by presenting an overview of the analysis and the background resources used to show the development of those TRs and TSs. This Technical Report provides a general overview of a key set of indicators related to the use of information and communication technology (ICT) and corresponding impacts on city sustainability in smart sustainable cities (SSC). It is intended for an audience of SSC decision‐makers and strategists, interested in gaining a more in‐depth understanding of existing knowledge and approaches to indexes and KPIs for SSC. This Technical Report illustrates the vast body of resources gathered on the evaluation index systems of smart cities and KPIs for sustainable cities, among others, that served as a background for the development of related series of KPIs Technical Reports and Technical Specifications. The resources presented in this Technical Report were analysed with respect to common elements, and a set of indicators focusing on ICT and its contribution to smart sustainable cites was developed.