Online reading has become an essential part of our life. Online reading has emerged as an active interdisciplinary field of scientific study in the past two decades. In order to develop a global view of the area, we conducted a bibliometric study on 7486 articles retrieved from WoS and Scopus databases published from 2004 to 2023. We analyzed the development trends in publications and citations, revealed the current major research themes, identified future research topics and most productive authors, affiliations, journals and countries. First, the publications and citations have been growing constantly in the past 20 years. Second, internet, e-book and comprehension have been the most frequently discussed topics. Third, three major themes have been revealed. The first theme emphasized the unique feature of online reading, which included the sub-themes of text features of hypertext, utilization of e-books, online health resources, and social interaction on line. The second theme had to do with education and learning. The third theme was related to health literacy. Fourth, education and medicine would attract researchers' attention in future research. Finally, the USA leads the total publications in the area of online reading. Our study contributed to the theory building by providing a detailed understanding of online reading research from an international perspective. We used two databases, WoS and Scopus, and improved the development of search terms, data filtering and data analysis. Implications for researchers, scientists and educators were discussed.