One of the biggest challenges for open science data initiatives is identifying who is using data and for what. Without this information, it is difficult to understand the impact of scientific data and how to serve users better. As such, many assumptions and unknowns exist around Earth Science data use. The goal of this presentation is to share about OPeNDAP’s approach to learn more about its users. Such information can be used by other technical science-supporting organizations that seek to design their own user research programs, thereby improving their services and societal impact OPeNDAP, a nonprofit organization that hosts a protocol and open source software that enables users to access large Earth Science datasets, initiated a User Research program in 2023. They continue to learn about users by: Interviewing people in-person at domain-relevant conferences, workshops, and conventions. Analyzing emails that are sent to OPeNDAP’s support email address. Implementing a new structured online survey for collecting voluntary data. Using Google analytics to collect data about visitors of various OPeNDAP-supported websites. Before doing this work, we assumed that most OPeNDAP users were US-based, senior academics and researchers representing universities and governmental agencies, and doing mostly Earth science research. Our research results confirm that most OPeNDAP users are based in the US. However, the majority of people visiting OPeNDAP-supported websites are located internationally (70%). Many OPeNDAP users are mid-career and early career, indicating that OPeNDAP use is being perpetuated among new professionals. Inquirers do often represent mostly Universities, Federal Agencies, and National labs/Research centers, but the private sector was better represented than expected. Domain areas of inquirers included a much broader range than expected, including data applications for sustainable fisheries, maritime and shipping operations, pest and risk management, national security, and town administration. OPeNDAP’s User Research program provides the organization with valuable information about its users. Such information helps OPeNDAP better understand how its services and provided data are used in broader society, and make strategic decisions about new software features and business opportunities. [Poster SY21C-2443]