Usability evaluation plays a critical role in improving user experience and ensuring the quality of interactive systems. Although standardized tests are commonly used, they tend to evaluate usability in separate dimensions, resulting in partial and fragmented results. This article presents UnUQ (Unified Usability Questionnaire), a novel evaluation tool that integrates key ISO/IEC standards—25010, 25062, and 9241-11—along with Jakob Nielsen’s usability heuristics and well-established usability scales, including SUS, CSUQ, QUIS, and UMUX. The seven attributes that define UnUQ were identified through a clustering analysis of usability metrics, supported by a comprehensive literature review to ensure both conceptual soundness and theoretical grounding. Designed as a single instrument with 22 items, UnUQ provides a unified framework for evaluating core usability aspects, including effectiveness, efficiency, satisfaction, learning and memorability, accessibility, overall usability, and acceptance. Its purpose is to bridge the gap between formal standards and practical evaluation tools, thereby improving consistency and comparability of results across various digital environments.