Emerging development trends in smartphone computing assist the user to enhance skills, health improvement, earning opportunities, sharing ideas, providing entertainment, and so on. Appropriate transfer of these assistances demands a vibrant appearance to a smartphone user. End users emphasize easy-to-use, ergonomics, efficiency, and visual aesthetic, among others. Measuring usability issues allows for improving these features. An inspection-based heuristics set identifies the usability issues for improving the quality of smartphone interfaces. Using suitable heuristics is highly relevant. In this paper, we present an extended and relevant set of 14 Usability Heuristics for Smartphone (EUHSA) application, where 13 heuristics were selected after cross-linking the identified usability flaws with the previously proposed heuristics through a user study with 800 students from a human-computer interaction course. An additional heuristic is proposed against uncaptured usability flaws. Furthermore, the EUHSA was validated using an expert evaluation study. Findings were compared with the previously proposed Joyce and SMASH sets of heuristics. The results explicitly justify the EUHSA and prove its effectiveness in evaluating the usability issues.INDEX TERMS Human-computer interaction, usability experts, smartphone applications, heuristic evaluation, user interfaces.