How effectively and efficiently an individual user can achieve a specific goal through the use of an interface, product, or tool.

Five of the key criteria used to evaluate usability are learnability, efficiency, memorability, errors, and satisfaction.

5 quality components define usability:

  • Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
  • Efficiency: Once users have learned the design, how quickly can they perform tasks?
  • Memorability: When users return to the design after not using it, how easily can they reestablish proficiency?
  • Errors: How many errors do users make, how severe are these, and how easily can they recover from them?
  • Satisfaction: How pleasant is it to use the design?


ISO/TR 16980:2002 defines usability as the "extent to which specified users can use a product to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use."

These criteria evaluate how easily a user can learn to use a design, how quickly they can use it to achieve tasks, how well they can remember to use the design, what errors a user encounters and how they recover from them, and the quality of the user's experience overall.

Designing with accessibility in mind is one of the pillars of designing for usability, so proper consideration of usability should include usability for users with different usage needs.


Since they have similarities, accessibility is sometimes confused with usability. Usability is concerned with whether designs are effective, efficient and satisfying to use. Usability tends not to focus on the user experience of people with disabilities specifically.