Background Digital innovations have the potential to enhance current graduate medical education strategies. Objective We assessed the scope, reach, and effectiveness of Nephrology Simulator (NephSIM), a free, mobile-optimized, nephrology educational tool designed to teach pathophysiology with a diagnostic approach using interactive cases. Methods NephSIM, launched in June 2018, was designed as a mobile-optimized website with peer-reviewed content in WordPress. Content, including interactive cases with iterative feedback, infographics, and tutorials, was developed by nephrology fellows and attending nephrologists. The teaching tool was shared via an e-mail subscriber list and Twitter. Website usage data and Twitter analytics were reviewed. Case content was categorized, and the case completion rate was calculated. A self-report survey was sent to subscribers to assess their demographics and experience. Results Thirty-four cases have been published to date and represent a variety of nephrology topics. There have been 100 745 page views between June 2018 and June 2019, representing 17 922 unique visitors from more than 100 countries. There are 1929 accounts that follow NephSIM on Twitter. Tweets received 124 200 impressions and a 3% engagement rate. Median case completion rate was 69% (interquartile range 64%–78%). Our survey response rate was 17% (76 of 445). Nearly all NephSIM users rated the platform highly in terms of satisfaction and usability, and planned to continue using in the future. Conclusions The development of a mobile-optimized, case-based teaching approach by nephrology fellows and faculty is feasible and has demonstrated global participation and high levels of learner satisfaction.