Accessibility vs usability: What's the difference?

Portrait of Marie Moyles
By Marie Moyles

18 May 2022

For Global Accessibility Awareness Day, we look at the difference between accessibility and usability and how they both affect user experiences.

What is the purpose of Global Accessibility Awareness Day?

From the Global Accessibility Awareness Day website: “Every user deserves a first-rate digital experience on the web. Someone with a disability must be able to experience web-based services, content and other digital products with the same successful outcome as those without disabilities. This awareness and commitment to inclusion is the goal of Global Accessibility Awareness Day (GAAD), a global event that shines a light on digital access and inclusion for people with disabilities.”

How do we achieve digital accessibility?

Accessibility is a facet of user experience design. Achieving digital accessibility does not rely on standards and guidelines alone. It is not just adhering to a checklist of requirements. Taking this approach will only get us so far.

To provide a good experience for the broadest range of users we need to ensure that what we design is:

  • accessible
  • usable
  • useful
  • desirable
  • valuable
  • findable
  • credible

The two facets I will focus on for this post are accessible and usable.

What do we mean by digital accessibility?

When creating accessible digital products and services we are ensuring that people with a range of impairments can perceive, understand and navigate content and functionality in the absence of barriers.

As designers and developers we need to understand that the way we create and build our products may create barriers for users. We need to always think of those who have the following impairments:

  • visual
  • auditory
  • physical
  • speech
  • cognitive
  • neurological

Web Content Accessibility Guidelines

Adhering to the Web Content Accessibility Guidelines (WCAG) helps us avoid creating barriers for accessibility.

Currently, public sector websites are legally bound by the Public Sector Bodies (Websites and Mobile Applications) (No. 2) Accessibility Regulations 2018 to be accessible for everyone to use. Meeting these regulations is done by adhering to WCAG at Level AA.

Level AA is seen to address the most common barriers for disabled users. At this level, websites are considered to be usable and understandable for most people.

The next level up from this is Level AAA and offers the highest level of compliance. At this level, websites are considered to be accessible to the greatest number of people with disabilities.

What do we mean by usability?

The International Standards Organisation’s standard ISO9241, defines usability as: “the effectiveness, efficiency and satisfaction with which specified users achieve specified goals in particular environments”

A product is seen as usable when it:

  • allows a user to complete a goal with precision and in total completeness (effectiveness)
  • provides the resources necessary to complete these goals in an effective way (efficiency)
  • allows a user to feel comfortable using the product to achieve their goals (satisfaction)

Where usability and accessibility intersect

In general, building an accessible product usually means improved usability for most users.

I enjoy digital products which have:

  • responsive design applied which allows for magnification without the loss of content
  • well considered colour contrast especially when using a screen with poor display brightness
  • captions on various forms of media
  • good keyboard accessibility when filling out forms

However, for disabled users it can be true that a product or a site technically classified as ‘accessible’ under the WCAG criteria can still provide a poor user experience.

Without considering the 3 core components of usability (effectiveness, efficiency and satisfaction), disabled users can end up at a disadvantage.

"A product or a site technically classified as ‘accessible’ under the WCAG criteria can still provide a poor user experience."

Case study: testing links with blind participants

We tested a website with pages containing up to 80 links with a blind participant.

The page was technically accessible as all the links were unique and descriptive. For our blind participant, hearing that there were 80 links reduced their ability to effectively complete their task.

Having too many links impacted on the efficiency of navigating the page for the participant. This resulted in diminished levels of satisfaction for the participant. Navigating a page via links was their preferred way of gaining an understanding of a page.

Having to change their normal behaviour meant that their overall user experience was unpleasant. It meant that they would be reluctant to explore the rest of the site as the concern was they would be presented with similar amount of links on different pages of the site.

Designing for usability

Designing against checklists informed by guidelines and standards is an excellent foundation on which to build accessible digital experiences. However, we are usually working towards compliance against WCAG 2.1 Level AA.

We need to be conscious that the criteria which impacts on a key area for usability - the creation and governance of content - falls under Level AAA. These criteria cover areas such as:

  • unusual words
  • idioms and jargon
  • abbreviations
  • reading level
  • section headings

If working towards WCAG 2.1 Level AA compliance, these criteria will be omitted from an accessibility audit making the site technically accessible. But the site will be potentially unusable for certain audiences.

For example, a screen reader user may be able to navigate a page by the use of headings. But if abbreviations and jargon are used without explanation the purpose of the content is lost. This then could potentially undermine the user’s ability to complete a task on the site.

So, when designing a product or service we can:

  • review our designs to ensure that we are understanding the needs of the users who are expected to rely on the product
  • ensure that we use tested components we are confident are functionally and technically accessible
  • test the flow of the product or site built with accessible components with a variety of users of different levels of impairment
  • ensure content is specific, well curated and governed

These steps will go a lot further in achieving a consistently brilliant and enjoyable user experience for a lot more people.