A Heuristic Evaluator developer conducts heuristic evaluations, which are usability inspections of a user interface design, based on a set of predetermined principles or heuristics. Their role includes identifying design flaws, evaluating the severity of usability problems, and recommending improvements. They examine each element of the user interface, ensuring it aligns with established usability principles, such as visibility of system status, consistency, and error prevention. This process aids in enhancing the user experience, improving product functionality, and reducing development costs by identifying potential issues early in the design process.