Often used in the same context, Usability’ and ‘Accessibility’ are terms that can be misused and confused.
Usability can be precisely defined, however accessibility has many different approaches and meanings.
Usability focuses on how intuitive and easy it is for all people to use. Usable designs are consistent and simple to learn to use. Usability and accessibility often are complimentary.
In terms of web design, Usability can be defined by five quality components:
Learnability
How easy is the website to use?
Memorability
Will visitors remember how to use the site on their next visit?
Effectiveness
Can visitors easily navigate through the site, determine what to do next and understand the content?
Efficiency
Can visitors find what they want in a reasonable time?
Satisfaction
How enjoyable is the site to use?
Accessibility is determined by how barrier free the technology is. Accessibility problems are those that make it more difficult for persons with disabilities to use an application or service than for a non-disabled person. It’s possible for a site to be accessible and not usable, and vice versa – a site could be usable but not accessible.
The World Wide Web Consortium defines web accessibility as an attribute through which “people with disabilities can perceive, understand, navigate, and interact with the web, and they can contribute to the web”. Web accessibility includes all types of disabilities that impact access to the web and thus includes visual, auditory, physical, speech, cognitive and neurological disabilities and adherence to web accessibility principles also benefits elderly users.
