{Reference Type}: Journal Article {Title}: A Quarter-Century of Online Informatics Education: Learners Served and Lessons Learned. {Author}: Hersh W; {Journal}: J Med Internet Res {Volume}: 26 {Issue}: 0 {Year}: 2024 Aug 6 {Factor}: 7.076 {DOI}: 10.2196/59066 {Abstract}: The value and methods of online learning have changed tremendously over the last 25 years. The goal of this paper is to review a quarter-century of experience with online learning by the author in the field of biomedical and health informatics, describing the learners served and the lessons learned. The author details the history of the decision to pursue online education in informatics, describing the approaches taken as educational technology evolved over time. A large number of learners have been served, and the online learning approach has been well-received, with many lessons learned to optimize the educational experience. Online education in biomedical and health informatics has provided a scalable and exemplary approach to learning in this field.