Usability measures the quality of a user's experience when interacting with a product or system - whether a Web site, a software application, mobile technology, or any user-operated device.

In general, usability refers to how well users can learn and use a product to achieve their goals and how satisfied they are with that process. Usability, as defined by Joseph Dumas and Janice (Ginny) Redish, means that people who use the product can do so quickly and easily to accomplish their tasks. Usability may also consider such factors as cost- effectiveness and usefulness.

A key methodology for carrying out usability is called User - Centered Design.