Presentation from Open Science: Monitoring Progress, Assessing Impact conference held 7–8 July 2025 at UNESCO Headquarters in Paris and online. Annotation: How can we tell whether Open Science is making a difference? This opening session shared key insights from PathOS, a three-year EU project investigating how Open Science affects research, society, and the economy. It begin with an overview of the project’s evidence, methods and tools. A panel discussion then reflects on real-world case studies, what they revealed, what was unexpected, and what remains unclear. As the conference marking the final public event of PathOS gets underway, this session set the tone by combining strategic insight with grounded reflections on how Open Science is and can be monitored in practice. Learn more about the conference and check out other presentations here: https://pathos-project.eu/conference-on-open-science-monitoring-progress-assessing-impact