Africapolis data is based on a large inventory of housing and population censuses, electoral registers and other official population sources, in some cases dating back to the beginning of the 20th century. The regularity, the detail and the reliability of these sources vary from country to country, and from period to period. Satellite and aerial images are used to inform on the physical evidence on the ground, that is the built-up area and the precise location of settlements. Other official cartographic resources, such as administrative boundaries, are used to link population data to the observed information on the built-up areas. The teams working on Africapolis, at e-Geopolis and at the OECD Sahel and West Africa Club, have for years worked on building the Africapolis database, learning during the process, adding new sources and improving on the tools and methodology used to make the data as precise as possible. However, the single most important element is official population records, the census data. In certain cases the last available records date back 30 or more years and often more than ten. Given the pace of demographic and urban dynamics these are significant periods. Africapolis, like e-Geopolis globally, has been designed to provide a much needed standardised and geospatial database on urbanisation dynamics in Africa, with the aim of making urban data in Africa comparable across countries and across time. This version of Africapolis is the first time that the data for the 50 countries currently covered are available for the same base year – 2015. In addition, Africapolis closes one major data gap by integrating 7 225 small towns and intermediary cities between 10 000 and 300 000 inhabitants (6 737 urban agglomerations between 10 000 and 100 000 inhabitants for a total of 180 million people). Africapolis will remain an on-going endeavour, providing data and evidence to support cities and governments to make urban areas more inclusive, productive and sustainable. We will keep looking for new ways, new tools and new data to improve Africapolis and its relevance for the African continent and invite you to contribute.