Few studies have investigated the urban morphology of informal settlements at fine-grain level, limiting effective urban planning and policies targeting such areas. This study presents a high-resolution morphological analysis of five informal settlements located in central areas of major cities in East Africa. The analysis is based on indicators of urban form, statistical comparison, and field interviews on household conditions. The method improves the replicability and increases the spatial granularity compared to previous studies. Outcomes show that all case studies are characterised by organic street layouts. Three settlements form a comparable group with denser urban fabrics (small block size, high coverage ratios, and small private spaces), while the remaining two cases have less compact forms. The field interviews show high rates of tenancy, overcrowding, and inadequate access to water and sanitation in the first group and low rates of these conditions in the second group. We suggest that these differences are partially an outcome of levels of informal land supply. We argue that decreased informal land supply leads to increased competition and higher prices of accommodation, leaving fewer household resources for infrastructure investments and consequent compromised livelihoods. Accordingly, we argue that some modes of informal urban development should be accepted in Sub-Saharan Africa.