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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This is an outdated draft and should not be referenced or quoted.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 a clear distinction between them. [delete this? 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 people with disabilities from using the website.] The overlap is especially strong when considering the needs of older people with ageing-related impairments and people with cognitive disabilities.

In most situations there is no need to define and differentiate between usability and accessibility, such as when designers are creating a website. However, there are times when the distinction between accessibility and usability is important, such as when defining specific accessibility standards and policies.

This page explores the distinction between accessibility and usability in the context of web accessibility standards, guidelines, and conformance, as well as research. It addresses some questions and misunderstandings about making websites accessible and usable by people with disabilities.

Accessibility as Focused Usability

International Organization for Standardization (ISO) 9241-11 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." [@] Using this definition, one could say that accessibility focuses on:

Put more simply:

With most websites, the users can be anyone in the world, in all sorts of situations. Thus it is vital that the focus of usability is appropriately broadened.

Differentiating for Accessibility Standards and Guidelines

More distinction is needed to clarify what should be included in accessibility standards, from what is general usability and should not be included in accessibility standards.

One way to start looking at the distinction between the two is to categorize interface problems:

Another way to look at it is that accessibility is about avoiding and removing barriers that prevent people from using the website, product, or service. In this way, accessibility is a precursor to usability, that is, an interface cannot be usable (to people with disabilities) until i

The distinction between usability and accessibility is especially difficult to define when considering the needs of older people with ageing-related impairments, and considering cognitive and language disabilities. Many of the accessibility guidelines to improve accessibility for people with cognitive disabilities are the same as general usability guidelines. Guidelines to design websites for older users often cross the line between usability and accessibility.

The distinction is important where there are significant requirements for accessibility, for example, national regulations requiring that websites not discriminate against people with disabilities.

Defining Responsibilities for Accessibility

[is this out of scope for this document - or important and not covered elsewhere, so we'll put it here? say something here, or just in the FAQ section?]

"Technical Accessibility" and "Usable Accessibility"

... @@ meets standards but designer didn't have understand of how people with disabilities use the web and did some stupid things; therefore, not a degree of usability for people with accessibility needs. sometimes this is called "usable accessibility"... see question Can a website meet accessibility standards and be technically accessible, but not be really usable by people with disabilities? below....

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]

Questions and Misunderstandings

[for EOWG discussion: issue with stating a myth/misunderstanding/illegitimate question put it in people's head... however, if don't people might miss it all together.]

intro@@ ... answers below assume comprehensive standards WCAG 2.0. Some answers do not apply to other standards, for example, the old U.S. Section 508 standards that do not cover all accessibility issues. @@answers these questions:

Can a website meet accessibility standards and be technically accessible, but not be really usable by people with disabilities?

@@ if understand issues and meet spirit of the standards, will be pretty usable... you could *try* and purposely do this... usability goes beyond accessibility... if you don't understand basics issues of how pwds use web, you could design site that meets technical requirements but does stuff stupidly and makes it hard for pwds to use it, e.g., verbose alt text on decorative images [ref: too much accessibility]. also answer: "When does such poor usability make a website not practically accessible by people with disabilities (even if "technically accessible")?"

Can a website be usable by people with disabilities, but not meet accessibility standards (not be "technically accessible")?

@@ can be accessible to some pwds but not meet standards, and not be accessible to other pwds. generally, if a site is accessible to a people with a range of different types of disabilities, it will meet standards each requirement std has a reason for existing, and thus if the website doesn't meet one aspect of it, it's probably not accessible to someone... but there could be a minor exception here & there... this is applies for WCAG 2.0 - for other standards maybe not so much...

Does designing a site for optimum "usable accessibility" compromise usability for people without disabilities?

@@... if you design for optimum usable accessibility for all types of disparities, it will be highlight usable for people without disability. If you optimize a site for only one type of disability, it might be less usable for people without that disability, including people with other disabilities and people without disabilities...

Do "usable accessibility" requirements conflict for people with different disabilities?

[(for example, website developer: "some people say my site has too many links/ too much information, but then they don't want me using javascript to create expanding menus for progressive disclosure") ("I used used XYZ fancy feature to put my 100s of links in a nice widget, but then people complained it's not accessible to screen readers. But then I put all the links in nested lists and people complained it's too much for people with cognitive disabilities.) Issue: The problem is not inherently accessibility, here, it's usability - you have too many links not well organized.]
@@... 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...

Some accessibility features aren't available in some browsers and assistive technologies. Should the website have to compensate?

@@... 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...

[What aspects of website accessibility and usability are web developers responsible for, versus browsers and assistive technologies. (for example, website developer: "If the browsers and AT don't do their job well, I shouldn't have to compensate for it, should I?") (for example: should websites have a text resize widget?)
[I think when we talk about accessibility/usability then we also need to briefly mention the context such as browsers and Web technologies. For instance, that HTML does not (yet) provide sections markup, so that the header elements have to be (mis-)used for that purpose. That is getting technical but messaging that "designers may need to compensate for the lack of usability in the browsers and technologies" is important.]
[@@it is about browsers not being usable and therefore website developers sometimes need to compensate for it. This is quite apparent for older people and others who are new to computer but not really an accessibility issue per se. If you are writing guidelines for developers making websites accessible, should they include compensations for browser and AT inadequacy?]
[Another complication when defining accessibility standards and guidelines is the responsibilities of the browsers and other components of web accessbilty.]

What if a feature that will improve usability for some users cannot be made accessible (e.g., an Ajax widget)?

@@ provide accessible option, and provide option of the more usability interface - progressive enhancement (gracefully degradation)...

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.[@]