In the world of eLearning, HTML5 is being hailed as the wave of the future. Since HTML5 is the new standard, eLearning professionals must get on board and begin using it to collaborate with other professionals and eLearning content developers. Businesses and educational institutions seeking online training will increasingly choose HTML5 courses over Flash because of the incredible compatibility opportunities and ease of authoring, which means they'll be searching for eLearning practitioners who are familiar with HTML5 resources. Because of its high degree of interactivity, immersive visuals, and engaging animations, Adobe Flash was once one of the most common authoring resources for eLearning courses. HTML5, a mobile-friendly option, is becoming the new choice among eLearning professionals as fewer smartphones and tablets will support Flash. However, the support for the Flash player has been discontinued by Adobe by the end of 2020, for most of the online platforms. And hence it is high time for the eLearning content developers and educators to think about the latest trends in education technology. Interactive Multimedia based authoring for eLearning will be very versatile if done using HTML5. This research paper reviews requirements and implementation of such eLearning tools for Online Teaching and Learning. This is especially needed in situations like the ongoing COVID-19 pandemic when most of the schools and higher education institutions have moved to adapt eLearning and online mode of teaching and learning.