# Usability Usability is a quality attribute that measures how easy and efficient a product is to use. Defined by [[Jakob Nielsen]], usability encompasses learnability, efficiency, memorability, errors, and satisfaction. It's a core component of [[User Experience (UX)]] but focuses specifically on task completion rather than the broader emotional experience. Good usability means users can accomplish their goals quickly, with minimal errors, and without frustration. Unlike [[Accessibility (a11y)]] (which ensures products work for people with disabilities), usability applies to all users—though the two overlap significantly. Usability testing, where real users attempt tasks, remains the gold standard for evaluation. ## Nielsen's Usability Components | Component | Description | |-----------|-------------| | **Learnability** | How easy for first-time users? | | **Efficiency** | How fast for experienced users? | | **Memorability** | How easy to remember after absence? | | **Errors** | How many errors, how severe, how recoverable? | | **Satisfaction** | How pleasant to use? | ## Nielsen's 10 Usability Heuristics 1. Visibility of system status 2. Match between system and real world 3. User control and freedom 4. Consistency and standards 5. Error prevention 6. Recognition rather than recall 7. Flexibility and efficiency of use 8. Aesthetic and minimalist design 9. Help users recognize, diagnose, and recover from errors 10. Help and documentation ## Usability Testing Methods - **Think-aloud protocol**: Users verbalize thoughts while performing tasks - **Task analysis**: Measure time and success rates - **A/B testing**: Compare two versions with real users - **Heuristic evaluation**: Experts evaluate against principles - **Eye tracking**: See where users look - **First-click testing**: Where do users click first? ## Key Metrics - **Task success rate**: Percentage completing tasks - **Time on task**: How long tasks take - **Error rate**: Mistakes per task - **System Usability Scale (SUS)**: Standardized questionnaire - **Net Promoter Score (NPS)**: User satisfaction ## References - https://www.nngroup.com/articles/usability-101-introduction-to-usability/ - https://www.nngroup.com/articles/ten-usability-heuristics/ - Jakob Nielsen: *Usability Engineering* (1993) ## Related - [[Jakob Nielsen]] - [[User Experience (UX)]] - [[User Interface Design]] - [[Accessibility (a11y)]] - [[Human-Computer Interaction (HCI)]] - [[Don Norman]]