This report explores the impacts of Open Science (OS) practices with the scope of a proof-ofconcept study using the impact pathway concept described in PathOS D1.1 (Dekker et al., 2023). Based on previous data collected by PathOS, particularly from the scoping review by Klebel et al. (2024) and empirical case studies conducted by Cole et al. (2023), this report customizes, tests, and validates the Key Impact Pathway (KIP) approach in the context of Open Science. The approach utilises evaluation methods and concepts, particularly identifying impact chains (from activities to the creation of outputs, outcomes, and impacts) and collects and codes information from a set of 40+ sources. The resulting information is used to generate high-level impact chains, displayed as intervention logics, of Open Science practices. Three such preliminary pathways indicating the impacts of different Open Science activities are identified in the report: 1) Citizen Science, 3) Open Access pathway, 3) Impacts on climate and environment. These were selected based on the availability of relevant evidence: A Citizen Science pathway was constructed based on the selection of ‘citizen science’ using a “downstream analysis” - starting from intervention and moving downstream to impacts. The pathway illustrates how citizen science interventions correlate with certain impacts such as ‘trust’ stemming from the outcome of engagement of citizens in citizen science projects. An Open Access pathway was likewise constructed through a “downstream” analysis and provides an initial view how availability of open access publication’s (output) relates to aspects such as novelty (outcome), quality (impact), reproducibility (Impact). Impacts of Open Science on climate and environment were identified through an“Upstream analysis” – starting from impact and moving upstream to relevant interventions. The approach tested whether selecting a given impact would yield an overview of the individual steps and effects leading to this type of impact. The findings illustrate the important mediating factor of policy and governance, which can be affected by a broad range of societal aspects. This deliverable set out as a proof-of-concept of the applicability of the KIPs framework for Open Science and the results indicate that that the approach works in principle and can be scaled up, allowing the identification of additional pathways and the refinement of the existing ones. Both tracing the effects of different Open Science interventions up to the impact stage (“downstream analysis”) and identifying the activities that may create certain academic, societal, and economic impacts (“upstream analysis”) are feasible. The next steps involve several actions within the PathOS project. The evidence base will be expanded by integrating more documents and sources, with a careful selection and coverage of topics, with an updated data extraction template. The remaining PathOS case studies will be integrated as well. Efforts will be made to refine the representations and reporting of impact pathways. Focus will be on enhanced contextual explanations and explicating assumption, including their limitations and broader socio-economic contexts. * This project deliverable is currently pending approval by the EC.