What is Usability?
Usability is a quality attribute that describes how easy it is for users to use an interface. According to ISO 9241, usability encompasses: effectiveness (Can users achieve their goals?), efficiency (With how much effort?), and satisfaction (How pleasant is the experience?). Good usability means: intuitive navigation, clear labels, consistent design, fast loading times, and helpful error messages. Usability is measured through user tests, heatmaps, session recordings, and metrics like task completion rate. Jakob Nielsen defined 10 usability heuristics as evaluation criteria.
Key Points
- 3 dimensions: Effectiveness, efficiency, satisfaction
- Nielsen's 10 usability heuristics as checklist
- Usability testing with real users
- Think-aloud protocol: Users verbalize thoughts
- 5-second test: Is the purpose immediately clear?
- Heatmaps show click and scroll behavior
Practical Example
“After usability testing, we simplified checkout from 5 to 3 steps - abandonment rate dropped by 40%.”