This W3C Draft Note provides an introduction to use of the Web by
people with a variety of disabilities, for the purpose of better understanding
their requirements when Web sites and Web-based applications. It is a supporting
document for guidelines and technical work of the W3C
Web Accessibility Initiative (WAI).
Specifically, this document describes requirements for Web access by people
with physical, visual, hearing, and cognitive or neurological disabilities;
it describes assistive technologies used by some people with disabilities
when accessing the Web; and it provides examples of people with disabilities
successfully or unsuccessfully accessing the Web according to the designs
of Web sites and Web-based applications. This document is not intended as
a comprehensive or in-depth description of disability, nor of assistive
technologies used by people with disabilities.
This document is [not yet] a W3C Note made available by the W3C
Web Accessibility Initiative. This NOTE
has [not yet] been jointly approved by the WAI
Education and Outreach Working Group (EOWG), the
Web Content Guidelines Working Group, the
User Agent Guidelines Working Group, the
Authoring Tool Guidelines Working Group, and the
Protocols and Formats Working Group (PFWG). This version
is offered for EOWG review and has [not yet] been reviewed by all listed
Publication of a W3C Note does not imply endorsement by W3C membership. A
list of current W3C technical reports and publications, including working
drafts and notes, can be found at
NOTE: This draft has been re-edited through the end of Section one, "How
Different Disabilities Affect Access to the Web." Section two is not edited,
and section three has not been added yet.
NOTE: This document has been modified after its original date of publishing
to correct the "Latest Version" URI.
1. How Different Disabilities Affect Access to the Web
This section describes several general groupings of disabilities, and how
they affect access to the Web. There are no universally accepted or absolute
categorizations of disability. Disability terminology varies from country
to country, and between different disability communities in the same country.
Abilities can vary from person to person, or over time, for different people
with the same kind of disability. People can have combinations of different
limitations, such as a visual and hearing disability together. This particular
combination of disabilities is described below.
The term "disability" itself is also used very generally in this document.
Many people with conditions described below would not consider themselves
to have disabilities; they may, however, have limitations related to sensory,
physical or cognitive functioning which can affect access to the Web. Limitations
can include injury-related and aging-related conditions, and can be temporary
,or chronic. An example of an injury-related limitation that is temporary
for some people and chronic for others repetitive stress syndrome. There
is a trend in some communities away from using medical terminology to describe
disability, and a trend in many communities away from using negative terminology
or epithets frequently used in the past. This Draft Note does not
attempt to comprehensively address these issues of terminology.
Different disabilities sometimes require similar accommodations. For instance,
both someone who is blind and someone who cannot use his or her hands require
full keyboard support for the commands in browsers and authoring tools, since
they both have difficulty using a mouse but can use different assistive
technologies to activate commands that are supported by a standard keyboard
The number and severity of disabilities tend to increase as people with age,
and may include changes in vision, hearing, memory, or motor function, which
can be accommodated on the Web as with any other disabilities.
Many of the accessibility solutions described in this Note contribute to
"universal design" or "design for all" by benefiting non-disabled users.
For example, support for speech output not only benefits blind users, but
also Web users whose eyes are busy with other tasks; while captions of audio
not only benefit deaf users but also increase the efficiency of indexing
and searching audio content on Web sites.
Solutions for the barriers to Web site accessibility described in this section
are available in the Web Content
Accessibility Guidelines 1.0. Solutions for browser accessibility are
available in the User Agent Accessibility
Guidelines, and for authoring tool accessibility in the
Authoring Tool Accessibility Guidelines.
Blindness involves a substantial uncorrectable loss of vision in both eyes.
To access the Web, most individuals who are blind rely on screen readers
(software that reads text on the screen with a synthetic voice) and/or
refreshable braille displays (a device that dynamically displays lines of
text on the screen in braille). Some people who are blind prefer text-based
browsers to graphical browsers.
Barriers that people with blindness may encounter on the Web include:
images that do not have alt text
complex images (e.g., graphs or charts) that are not adequately described
video that is not described in text or audio
tables that do not make sense when read serially (in a cell-by-cell mode)
frames that do not have "NOFRAME" alternatives, or that do not have meaningful
forms that cannot be tabbed through in a logical sequence, or that are poorly
browsers and authoring tools that lack keyboard support for all commands
browsers and authoring tools that do not use standard applications programmer
interfaces for the operating system they are based in
There are many types of low vision, including poor acuity (vision that is
not sharp), tunnel vision (seeing only the middle of the visual field),
central field loss (seeing only the edges of the visual field), and clouded
To use the Web, some people with low vision use extra-large monitors and
increase the size of system fonts and images. Others use screen magnification
or screen enhancement software. Some individuals prefer specific combinations
of text and background colors, such as a 24-point bright yellow font on a
black background, or choose certain typefaces that they find especially legible.
Barriers that people with low vision may encounter on the Web include:
Web pages with absolute font sizes that do not enlarge easily
Web pages that, because of inconsistent layout, are difficult to navigate
when enlarged, due to loss of surrounding context
browsers that do not support user override of authors' style sheets
Color blindness is a lack of sensitivity to certain colors. Common forms
of color blindness include difficulty distinguishing between red and green,
or between yellow and blue. Sometimes color blindness results in the inability
to perceive any color.
To use the Web, people with color blindness may use their own style sheets
to override the font and background color choices of the author.
Barriers that people with color blindness may encounter on the Web include:
color that is used as a unique marker to emphasize text on a Web site
text that inadequately contrasts with background color or patterns
browsers that do not support user override of authors' style sheets
Deafness involves a substantial uncorrectable impairment of hearing in both
ears. Some deaf individuals' first language is a sign language, and they
may or may not be fluent readers of a written language.
To use the Web, people who are deaf may rely on captions for audio content.
Barriers that people who are deaf may encounter on the Web include:
lack of captions or transcripts for audio content on the Web
lack of visual signposts in pages full of text, which can slow comprehension
for non-native readers of a written language
Hard of hearing
A person with a mild to moderate hearing impairment may be considered hard
To use the Web, people who are hard of hearing may rely on captions for audio
content together with amplification of audio.
Barriers encountered on the Web include:
lack of captions or transcripts for audio content
Motor disabilities can include weakness, limitations of muscular control
(such as involuntary movements, a lack of coordination, or paralysis),
limitations of sensation, joint problems, or missing limbs. Some physical
disabilities can include pain which further impedes movement. Any of these
conditions can affect the hands and arms as well as other parts of the
To use the Web, people with disabilities affecting the hands or arms may
use a specialized mouse; a keyboard with a layout of keys that matches their
range of motion; a head-mouse, head-pointer, or mouth-stick; voice-recognition
software; an eye-gaze system, or other assistive technologies to access and
interact with the information on Web sites. They may activate commands by
using single keystrokes rather than the simultaneous keystrokes needed to
activate commands in some applications. They may need more time when filling
out interactive forms on Web sites.
Barriers that people with motor disabilities affecting the hands or arms
may encounter include:
browsers and authoring tools that do not support serialized keystrokes for
forms that cannot be tabbed through in a logical order
interactive forms with time-limited response options
Speech disabilities can include difficulty producing speech that is recognizable
by some voice recognition software, either in terms of loudness or clarity.
To use parts of the Web that are beginning to rely on voice recognition,
someone with a speech disability needs to be able to use an alternate input
mode such as text entered via a keyboard.
Barriers that people with speech disabilities encounter on the Web include:
Web sites that require voice-based interaction and have no alternative input
Cognitive and Neurological Disabilities
Individuals with learning disabilities may have difficulty processing written
language or images when read visually, or spoken language when heard, or
numbers when read visually or heard. Specific learning disabilities can affect
the ability to focus.
To use the Web, people with learning disabilities may rely on getting information
through several modalities at the same time. For instance, someone who has
difficulty reading may use speech output to facilitate comprehension, while
someone with an auditory learning disability may use captions to help understand
an audio track. An individual who is highly distractible may need to turn
off animations on a site in order to be able to focus on the site's
Barriers that people with learning disabilities may encounter on the Web
lack of alternative modalities for information on Web sites, for instance
lack of alternative text that can be converted to audio to supplement visuals,
or the lack of captions for audio
distracting visual or audio elements that cannot easily be turned off
lack of clear and consistent organization of Web sites
Impairments of intelligence
Some individuals learn more slowly or have difficulty understanding complex
To use the Web, people with impairments of intelligence may take more time
on a Web site, may rely more on graphics to enhance understanding of a site,
and may benefit from the level of language on a site not being unnecessarily
complex for the site's intended purpose.
lack of clear or consistent organization of Web sites
use of unnecessarily complex language on Web sites
lack of graphics on Web sites
Individuals may have memory difficulties for a variety of reasons: for instance
problems with short-term memory, missing long-term memory, or loss of language.
To use the Web, people with memory impairments may rely on a consistent
navigational structure throughout the site, and...
lack of clear or consistent organization of Web sites
Some individuals with seizure disorders are triggered by visual flickering
or audio signals at a certain frequency.
To use the Web, people with seizure disorders may turn off animations, blinking
text, or audio.
Avoidance of these visual or audio frequencies in Web sites prevents inadvertent
triggering of seizures. Barriers include:
use of visual or audio frequencies that can trigger seizures
Individuals with mental or emotional disabilities may have difficulty focusing.
To use the Web, people with psychiatric disabilities may turn off distracting
visual or audio elements.
lack of clear and consistent organization of a Web sites
distracting visual or audio elements
[not revised past this point]
The following is a list of assistive technologies that some people with
disabilities use to browse the Web. Assistive technologies are products used
by people with disabilities to help accomplish tasks that they cannot accomplish
otherwise or could not do easily otherwise. When dealing with the Web, assistive
technologies usually refer to adaptive software, specially designed hardware
devices, and/or standard devices used in alternative ways to provide access
for people with disabilities.
Some assistive technologies rely on output of other user agents, such as
graphical desktop browsers, text browsers, voice browsers, multimedia players,
Alternate keyboards or switches
Hardware or software devices, used by people with physical disabilities,
that provide an alternate way of creating keystrokes that appear to come
from the standard keyboard. Examples include on-screen keyboards, eyegaze
keyboards, and sip-and-puff switches. Applications that can be operated entirely
from the standard keyboard , with no mouse movements required, support
single-switch access or access via alternative keyboards.
Braille and refreshable braille
Braille is a technique involving six to eight dots that are raised in different
patterns to represent letters and numbers so that they may be read by people
who are blind using their fingertips. Braille systems vary greatly around
the world. Some "grades" of braille include additional codes beyond standard
alpha-numeric characters, to represent common letter groupings (e.g., "th,"
"ble" in Grade II American English braille) to make braille more compact.
An 8-dot version of braille has been developed to allow all ASCII characters
to be represented. Dynamic or refreshable braille involves the use of a
mechanical display where dots can be raised and lowered dynamically to allow
any braille words to be displayed. Only letters and numbers can be represented
in braille, although some braille printers have a utility that allows simple
graphics to be drawn on a sheet using the raised dots at a resolution of
approximately 11 dots per inch.
Software used primarily by individuals with low vision that magnifies a portion
of the screen for easier viewing. Note that at the same time screen magnifiers
make presentations larger, they also reduce the area of the document that
may be viewed. Some screen magnifiers therefore offer two views of the screen:
one magnified and one default size for navigation.
Software used by individuals who are blind or have learning disabilities
that interprets what is displayed on a screen, and directs it either to speech
synthesis, for audio output, or refreshable braille, for tactile output.
Some screen readers use the document tree (i.e., the parsed document) as
their input. However, older screen readers make use of the rendered version
of a document, meaning that document order or structure may be lost (e.g.,
when tables are used for layout) and their output may be confusing.
Features of some operating systems that allow deaf or hard of hearing users
to receive visual notification that a warning or error sound has been emitted
by the computer.
Software used by individuals with some physical or cognitive disabilities
that highlights or announces selection choices (e.g., menu items, groups
of possible phrases, etc.) one at a time. A user selects a desired item by
hitting a switch when the desired item is highlighted or announced.
Voice recognition is used by people with some physical disabilities or temporary
injuries to hands and forearms -- as well as some users interested in greater
convenience, and as an input method in some voice browsers. Applications
that have full keyboard support can be used with voice recognition.
Examples of Accessibility and Inaccessibility on the Web
[Adapt Marja's "scenarios" here]
About the Web Accessibility Initiative
[Edit/update based on CSS boilerplate]
W3C's Web Accessibility Initiative (WAI) addresses accessibility of the Web
through five complementary activities that:
Ensure that the technology of the Web supports accessibility
Develop accessibility guidelines
Develop tools to facilitate evaluation and repair of Web sites
Conduct education and outreach
Conduct research and development
WAI's International Program Office enables partnering of industry, disability
organizations, accessibility research organizations, and governments interested
in creating an accessible Web. WAI sponsors include the US National Science
Foundation and Department of Education's National Institute on Disability
and Rehabilitation Research; the European Commission's DG XIII Telematics
for Disabled and Elderly Programme; IBM, Lotus Development Corporation, and
Additional information on WAI is available at
Web accessibility guidelines are essential for Web site development and for
Web-related applications development. WAI is coordinating with many organizations
to produce three sets of guidelines:
"Web Content Accessibility
Guidelines", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds. These
guidelines explain how to design accessible Web content.
"Authoring Tool Accessibility
Guidelines", J. Treviranus, J. Richards, I. Jacobs, C. McCathieNevile,
eds. These guidelines explain how to build accessible Web authoring tools.
"User Agent Accessibility
Guidelines", J. Gunderson and I. Jacobs, eds. These guidelines explain
how to design accessible user agents (browsers, multimedia tools, assistive
About the World Wide Web Consortium (W3C)
The W3C was created to lead the Web to its full potential by developing common
protocols that promote its evolution and ensure its interoperability. It
is an international industry consortium jointly run by the MIT Laboratory
for Computer Science (LCS) in the USA, the National Institute for Research
in Computer Science and Control (INRIA) in France and Keio University in
Japan. Services provided by the Consortium include: a repository of information
about the World Wide Web for developers and users; reference code implementations
to embody and promote standards; and various prototype and sample applications
to demonstrate use of new technology. To date, more than 320 organizations
are Members of the Consortium. For more information about the World Wide
Web Consortium, see http://www.w3.org/
Gregg Vanderheiden, Kate Vanderheiden, [add EOWG once reviewed, other WAI
groups once reviewed]
[Select a few key & stable references]