What is usability?

Usability means making products and systems easier to use, and matching them more closely to user needs and requirements.

The international standard, ISO 9241-11, provides guidance on usability and defines it as:

The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.

Usability is about:

• Effectiveness – can users complete tasks, achieve goals with the product, i.e. do what they want to do?
• Efficiency – how much effort do users require to do this? (Often measured in time)
• Satisfaction – what do users think about the products ease of use?

….which are affected by:

• The users – who is using the product? e.g. are they highly trained and experienced users, or novices?
• Their goals – what are the users trying to do with the product – does it support what they want to do with it?
• The usage situation (or ‘context of use’) – where and how is the product being used?

Usability should not be confused with ‘functionality’, however, as this is purely concerned with the functions and features of the product and has no bearing on whether users are able to use them or not. Increased functionality does not mean improved usability!

There are a series of international standards for usability and user centred design.