W3C logoWeb Accessibility Initiative (WAI) logo

WAI: Strategies, guidelines, and resources to make the Web accessible to people with disabilities

This is an outdated draft and should not be referenced or quoted.
The latest version is at: www.w3.org/WAI/intro/usable

[Early Rough Concept Draft] Relationship Between Web Accessibility and Usability

Page Contents


There is significant overlap between usability and accessibility, and not always a clear distinction between them. Usability is about making products easy to use. Accessibility focuses on designing products so that people with disabilities can use them, making sure there are no barriers preventing equal access.

In most situations there is no need to define and differentiate between usability and accessibility, such as when designers are creating a website. Usability approaches can be used to help implement accessibility requirements. In fact, accessibility can and should be part of the design and development process.

This page explores the relationship between accessibility and usability in the context of web accessibility standards, guidelines, and conformance. It highlights the overlapping benefits and addresses some questions about making websites and web tools accessible and usable by people with disabilities.

Diversity of Abilities and Situations

People have diverse abilities, skills, tools, and preferences. For instance, many people have different levels of auditory, cognitive, neurological, physical, speech, or visual disabilities, or combinations of these. People also have different levels of computer skills and use different approaches to access the Web. For instance, some people may not have access to certain computer software, including assistive technologies, because it is not affordable to them, because it is not installed on the computer they are using, because it is not available in their own language, or for many other reasons.

People with or without disabilities may also be in diverse situations which require them to use the Web in different ways. For instance, some people may be using the Web through mobile devices, television sets, or public terminals. They may be in loud environments so that they need alternatives to audio, they may be in bright sunlight so that they need high color contrasts, they may be unable to use pointing devices or their hands at all so that they need alternative input methods, or they may unable to download important images and multimedia due to broadband constraints.

The majority of these requirements overlap, and addressing the needs of one group of web users commonly benefits many others too. However, sometimes there are requirements that impact certain groups of users significantly more than they impact others. Accessibility standards define the requirements for people with disabilities, to avoid exclusion and discrimination. Most of these requirements benefit everyone, regardless of abilities, age, skills, education, languages, cultures, economics, and devices. They are an essential part of creating websites and web tools that are usable by everyone.

Defining Accessibility Requirements

In order to ensure equal access to websites and web tools, it is important to define accessibility requirements for people with disabilities. One way to start looking at the distinction between what should be included in accessibility standards, from what is general usability and should not be included in accessibility standards:

[Editor note: need to clarify re-use of the above citation, especially with the word "product" removed.]

The distinction is especially difficult to define when considering the needs of older web users, and considering cognitive and language disabilities. Many of the requirments to improve accessibility for people with cognitive disabilities are the same as general usability guidelines. Similarly, the needs of older web users often include general usability requirements in addition to accessibility requirements.

The Web Content Accessibility Guidelines (WCAG) 2.0, Authoring Tool Accessibility Guidelines (ATAG) 2.0, and User Agent Accessibility Guidelines (UAAG) 2.0 provide a stable set of accessibility requirements that can be met using different techniques. They also include advisory techniques that can be implemented in addition to the minimum requirements, to optimize accessibility to the widest audience possible.

It is important to maintain a unified set of technical requirements for web accessibility. The availability of such harmonized and internationally recognized accessibility standards accelerates the development of accessibility solutions and contributes to the availability of accessible websites and web tools. WAI invites contribution by providing feedback, developing additional techniques, or by actively participating in WAI.

Usability Beyond Accessibility

When designing products or services, including websites and web tools, it is usually more effective to avoid differentiating between accessibility and usability, and to develop for the widest audience possible. The International Organization for Standardization (ISO) defines usability as the "extent to which a product can be used by specified users to achieve specified goals effectively, efficiently and with satisfaction in a specified context of use" (ISO 9241-11). Using this definition, one could say that for most websites:

Put more simply:

Usability approaches and techniques, such as methods for analyzing design requirements, developing initial designs, and evaluating the user experience throughout the development process are essential for successful implementation of accessibility. In fact, trying to implement accessibility without considerations for the larger context of usability usually results in less optimal solutions for the developers and for the users.

@@@ for consideration here or elsewhere: trade-off in accessibility and usability

[@@@ ... usability is always a trade-off, e.g., making a website be easy to use and efficient for novice users versus expert users... flexibility of the web makes it easier (than designing hardware, e.g.) to design a site that will work well for different people in different situations...]

[@@@ ... in real world, you want to make your website accessibility, so sometimes do need to compensate. e.g., zoom feature and relative fonts, some people still have to use IE6 without zoom because that's all they are allowed to have on their corporate computer...]

Accessibility Highlights Usability

One of the many benefits of accessibility is improvement in general usability. Websites and web tools that are designed to be accessibility to people with disabilities have better usability for everyone.

Usability testing with participants with disabilities is particularly beneficial because many general usability issues are more apparent to users with disabilities. [participants with disabilities can be more effective in identifying general usability issues (that is, issues that affect people without disabilities as well).] General usability issues are often highlighted and easier to identify because the participants with disabilities are more sensitive to usability issues.[x] Using carefully selected participants with disabilities can more effectively find usability problems than using participants without disabilities.[x]

For example, @@

[answer: How do general usability issues impact people with disabilities more than people without disabilities?]

[point eval doc to this section]

References and Resources

[X] ISO 9241-11: Ergonomic Requirements for Office Work with Visual Display Terminals, Part 11: Guidance on Usability

[X] Introduction to Web Accessibility

[X] Understanding Web Accessibility

[X] "Distinguishing Between Accessibility and Usability Issues"

[x] FOCUS Project

Resources for More Information

[maybe list some, e.g., those in the Analysis page list, "yes, list them, this shows the history of the issue and gives it credibility"+1+1]

[draft notes not to lose]

Web accessibility means that people with disabilities can use the Web. More specifically, Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with the Web, and that they can contribute to the Web.[@]