DairyMix will use multi-criteria assessment, and develop decision support, modelling and management tools for sustainable circular mixed farming systems for dairy production. Dairy production systems (DPS) are an essential backbone of European agriculture. DPS produce high quality protein essential for humans. They can convert fibrous feed resources that could not be utilized by humans or converted to human food by monogastric animals. However, this desirable level of circularity is currently met only to a very limited extent with most dairy systems heavily relying on external input such as concentrate feeds and mineral fertilizers. DairyMix applies a systems approach for sustainable dairy production systems that are targeted to key European regions and beyond. DairyMix is structured in five work packages. WP1 is dedicated to coordination and management. Case studies, data from the extensive DATAMAN database, Eurostat data and data from OTICE, the online barn climate and emission control tool will be collected and analysed (WP2). Data analytics uses linear statistics as well as supervised machine learning algorithms, like ridge regression, random forests, support vector machines and artificial neural networks. Data analysis will assess the potential of currently known mitigation measures as well as the potential of precision farming technologies that are not yet fully developed. On farm decisions with respect to barn climate, emission reduction and improved animal welfare will be supported by the ICT-based tool OTICE. WP2 data are then fed into WP3 for detailed modelling analysis on carbon and nutrient utilization and circularity of mixed farming systems for dairy production. WP4 brings WP2 and WP3 together for a multi-criteria assessment of mixed farming systems for dairy production based on indicators for circularity and efficient resource use developed in WP2 and WP3. WP5 details a range of communication and dissemination activities and hosts the interactive web application - the MilKey/DairyMix platform - to analyse farm data and to evaluate effects of changes in farming practice at farm and regional level with regard to environmental, economic and societal sustainability indicators. This output will have farmers and other stakeholders in the primary sector as target group, and will also be relevant for society and policy makers. DairyMix will be a major step forward in achieving GHG mitigation and circularity between cropping systems and dairy production systems with flexible and context specific solutions being developed for key European areas and for Latin America. Extensive data collection, data analytics, and life cycle assessment and modelling will feed into the multi-criteria assessment to identify trade-offs and synergies and offer decision support for the exploitation of benefits while maintaining productivity and economic efficiency. DairyMix results will be made available by the MilKey/DairyMix multi-actor platform. The platform will not only be a valuable decision support tool for farmers, but will also follow a consumer-oriented approach to inform the consumer about concepts of circular and sustainable dairy production systems. The platform will provide context specific management strategies for key European regions and Latin America.