The United 4 Smart Sustainable Cities (U4SSC) Thematic Group published a first draft for the U4SSC Index - the index to measure the development of smart sustainable cities. The index, as presented in the draft, includes indicators for city planners to evaluate how ICTs have improved economic, environmental, and social aspects of their cities; according to the parameters of the 2030 Agenda for Sustainable Development. The indicators aim to provide cities with a consistent and standardised method to collect data and measure performance and progress to achieve sustainable development goals (SDGs); become a smarter and more sustainable city. Each indicator includes: (a) the rationale for choosing it; (b) how it should be interpreted; (c) which criteria are considered desirable; (d) the methodology for calculating the value to be reported; (e) possible sources of data. The information collected will be used by the ITU-T Study Group 20 (Internet of things, smart cities and communities) as part of its work to develop international standards for Internet of things (IoT) technologies and applications related to urban development challenges.