The PeerSharing project targets the sustainability of the use of internet platforms for sharing between private individuals. Four platforms were considered within the project: Kleiderkreisel for sharing of used / second-hand clothing, Drivy for private car rental, Flinc for carpooling and Wimdu for apartment sharing. User surveys were conducted to assess the consumption behaviour associated with platforms. The ecological effects of the behaviour changes induced by the use of the platforms were calculated using a mass flow model to conduct a life cycle analysis. The results are presented using global warming potential (GWP100) as an example indicator. Overall, a slight ecological advantage can be found for the platform use. Clothes-sharing has little ecological advantages, triggering the increased use of second-hand products but increasing overall consumption. There are clear advantages for carpooling through reducing emissions from mobility: The higher number of passengers per car lowers the individual emissions of each passenger. Some users of private car rentals and carpooling sold their cars, positively impacting their overall mobility emissions. Apart-ment sharing involves receiving travellers in private homes, reducing environmental impacts compared to hotel accommodation. However, much of the environmental impact of travelling is caused by the distance travelled (esp. air transport). Additional travelling encouraged by apartment sharing thus causes ecological disadvantages. The environmental potentials were extrapolated for the German population. The scenarios encompass a trend extrapolation and a sustainability assumption. Significant environmental potential lies in mobility behaviour. In general, the utilisation of the ecological potential depends on the consumer`s sustain-able orientation: additive consumption and a shift to ecologically damaging behaviour counteract the potential advantages of sharing. Financial effects from sharing activities on other consumption fields (financial rebound) were considered qualitatively within the scope of the project.