This study takes a closer look at platform-based digital business models and their implications for the economy and for society. While digital platforms have come to play a role in many branches of the economy, the present publication is focussed on the socio-politically most contested ones, namely digital labour platforms. These new platforms are increasingly beset by criticism. Usually they rely on a workforce of independent contractors, who work on their own account and at their own risk, for low wages and without social security. Neither the platform providers nor their clients take on the role and responsibilities of an employer. Labour laws, worker protection, health and safety regulations, quality of work and social security contributions mostly fall to the responsibility of the independent contractors alone, who are also not entitled to the kind of workers’ participation common in other sectors. The clients of the platforms essentially gain access to an on-demand workforce, while the independent contractors who provide the labour are subject to precarious working conditions. The study explains the basic mechanisms of three-sided digital labour markets and compares its variants and subcategories. It also explains the specific features and challenges of the different categories and proposes starting points for political measures. The study defines six basic types of digital labour platform. Under the category of cloud work (web-based digital labour) there are freelance marketplaces, micro tasking crowd work and context-based creative crowd work. The category of gig work (location-based digital labour) encompasses accommodation, transportation and delivery services (gig work), and household services and personal services (gig work).