Digital platforms are increasingly mediating how people seek and access housing. They offer powerful tools for property owners, landlords, agents, and tenants, to market and search for accommodation meeting particular criteria from price and tenure to location and dwelling characteristics (Boeing, 2020). These platforms range from generalist listing websites, such as Craigslist.org and Gumtree.com.au, to purposefully designed websites also known as ‘Proptech’ sector (Shaw, 2020), such as Realestate.com.au and Flatmates.com.au. Different platforms have different ‘platform logics’ (Fields and Rogers, 2021), business models and socio-technical structures to facilitate access to housing.

This paper mobilises a practice-based approach to understanding housing informality in Australian cities. The paper examines four platforms, including Realestate.com.au, Gumtree.com.au, Flatmates.com.au and Insiderairbnb.com.au, and the data they generate by using listings placed in August 2020, to provide insights into these housing markets and practices, focusing on the lesser-known or informal sector of the rental market, where conventional regulatory tenancy protections or housing standards are traded for lower cost accommodation. Using these datasets, we unearth a housing system ‘substructure’ of discrete types of informal tenure and dwelling, finding that each platform caters to a different type of platform housing informality.