The PathOS project on Open Science impact pathways aims to understand and demonstrate how Open Science—enabling research to be freely available, transparent, and inclusive—can create benefits for academia, society, and the economy. The project examined across three years three main questions: 1. What impacts does Open Science have? 2. How do those impacts happen? 3. What helps or hinders these impacts? We found that Open Science practices such as Open Access publishing, Open/FAIR Data, and Citizen Science are already reshaping research and its role in society. Our findings highlight: Academic Benefits: Open Science speeds up knowledge sharing, reduces duplication, and increases visibility of research through higher citation rates and broader reuse of data and methods. It also encourages collaboration across disciplines. However, benefits are uneven, with under-resourced researchers often left behind. Societal Benefits: Making knowledge freely available empowers communities, improves health and environmental outcomes, and strengthens trust in science. Citizen Science and other participatory approaches have proven especially effective at connecting research with real-world challenges. Economic Benefits: Open Science can reduce costs and speed up research production. Free access to data and tools saves money and time for researchers and companies, and in some cases contributes to new the development of new products and jobs. Still, the evidence here is patchy, and much of the claimed economic value is hard to prove directly. Access is not enough: Simply making research open does not guarantee impact. Quality, timing, and resources for both producers and users of knowledge are critical. Equity matters: Without careful design, Open Science may unintentionally widen gaps, favouring wealthier institutions and countries. Proof is tricky: While there are strong signals of impact, it is difficult to isolate the effects of openness from other factors such as funding, excellence, or timing. To strengthen the positive impacts of Open Science, PathOS recommends: Expanding support for open infrastructures (like repositories and data platforms). Ensuring equitable participation, so all researchers and communities can benefit, not just the well-funded. Focusing on quality and meaningful access, so that open outputs are reliable, reusable, and truly usable by diverse groups. Investing in better methods and evidence to understand, quantify and demonstrate impacts over time. Open Science has the potential to make research faster, fairer, and more useful for society and the economy. The PathOS project provides evidence-based pathways showing how these impacts occur and offers practical guidance to help policymakers, institutions, and researchers unlock its full value.