Street trading has become integral to how public space works in cities of the global South. It cannot be considered as marginal since it gears to the urban economy and works as a key mode of income generation for the urban poor to sustain livelihoods. A poor understanding of how forms of street trading work in public space can lead to poor design and policy interventions. While many practices of formalization aim at the elimination of informality, the challenge is to explore the complex informal/formal relations and the dynamics of street trading to understand how forms of informality negotiate space and visibility in the public realm. In this paper, we propose a typology of street trading, based on the criteria of mobility within public space and proximity to public/private urban interfaces. While exploring the degrees of mobility in informal street trading can be crucial to the modes of governance and adaptability involved, of critical importance is to investigate how street trading takes place in relation to the built form&mdash / particularly the edges of public space where public/private interfaces enable or constrain exchange and appropriation. The developed typology provides a better understanding of the dynamics of street trading and contributes to the ways in which the built environment professions can most effectively engage with interventions in public space without eradicating the scope for informal adaptations.