Abstract: Heuristic evaluation is a methodology used to inform developers of possible usability problems that can negatively impact on user experience. For the purpose of this study, the traditional set of heuristics by Nielsen’s principles (1994) together with more recent research inspired the development of domain specific heuristics developed in this study. The domain specific evaluation extend existing literature to prioritise 15 learning design principles that impact course design during teacher professional development. This includes a set of 24 heuristics and 49 evaluation foci. The aim of the research is to determine an appropriate set of heuristics to guide and examine the design of online interventions to demystify coding during teacher professional development instances. The practical implication is to evaluate an online training intervention using a set of heuristics to evaluate the potential design problems that could impact on the quality of the learning experience. The intervention under evaluation, which is an online website, targets office-based educators and teachers that want to understand how coding, robotics and computational thinking relate to education. The findings of this research provides a baseline for future design considerations for teacher professional development and more specifically with a focus on the conceptualisation of coding., M.Ed. (Information Communication Technology in Education)