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Use of the Web by People with Disabilities: Barriers, Assistive Technologies, and Usage Scenarios

W3C DRAFT NOTE 10-Sept-1999

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Latest Version:
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Judy Brewer (
Ian Jacobs (


This W3C Draft Note is a supporting document for guidelines and technical work of the W3C Web Accessibility Initiative (WAI). It provides an introduction to use of the Web by people with a variety of disabilities for the purpose of better understanding their requirements when using the Web.

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. Additional information on these topics is available by searching on the Web under many of the terms in this Note.

Status of this document

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 WAI EOWG review and has not yet been reviewed by all listed editors.

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 document has been modified after its original date of publishing to correct the "Latest Version" URI.

1. Barriers to Web Access Encountered by People with Disabilities

There are no universally accepted or absolute categorizations of disability. Terminology related to disabilities varies substantially from country to country, and also between different disability communities within the same country. People's abilities vary from person to person for the same type of disability, and often vary over time as well. This section describes several general categories of disability and how they relate to Web accessibility.

The term "disability" is used very generally in this document. Many people with conditions described below would not consider themselves to have disabilities, however they may have limitations related to sensory, physical or cognitive functioning which can affect access to the Web and therefore are described here. They may have experienced changes in several abilities due to aging. While some of the conditions described may be stable, or progressive, others are temporary -- for example, repetitive stress injury due to extensive keyboard use. There is a trend in some communities away from using medical terminology to describe disability, and a trend in many communities away from using the negative terminology or epithets frequently used in the past. This Draft Note does not attempt to comprehensively address these issues of terminology.

Note that different disabilities sometimes require similar accommodations, for instance, both an individual who is blind and an individual who cannot use his or her hands require full keyboard support for commands in browsers and authoring tools -- one because of inability to visually track the pointer, and the other because of inability to move the hands. At the same time, many accessibility solutions contribute to "universal design" by benefiting non-disabled users as well as disabled users -- support for speech output not only benefits blind users but also the Web user whose eyes are busy with another task; while captions of audio not only benefit the deaf user but also increase the efficiency of searching and indexing audio content on Web sites.

For each of the barriers described in this section, solutions are available in W3C's Web Content Accessibility Guidelines 1.0. A Checklist is available to test Web sites for accessibility, and an in-depth Techniques document in case any of the solutions recommended in the guidelines are unfamiliar.

Visual Disabilities

Blindness involves a substantial uncorrectable loss of vision in both eyes. To access the Web, individuals who are blind often rely on screen reading software, used in conjunction with graphical or text browsers, to drive speech output or refreshable braille output. Barriers they may encounter on the Web include:
  • images that do not have alt text
  • complex images such as graphs or charts that do not have extended descriptions
  • video that is not described in text or audio
  • tables that do not make sense when read serially, e.g. in a cell-by-cell mode
  • frames that do not have "no-frame" alternatives, or that do not have meaningful names
  • forms that cannot be tabbed through in a logical sequence
  • browsers and authoring tools that do not have keyboard support of all commands
Low Vision
There are many types of low vision. They include poor acuity (vision that is not sharp); tunnel vision (seeing only the middle of the visual field); peripheral vision (seeing only the edges of the visual field); clouded vision; etc. To use the Web, some people with low vision enlarge fonts and images slightly or substantially, and many use screen magnifying software to do this. Some individuals use specific combinations of text and background colors, for instance, 24-point bright yellow font on a black background, or use certain kinds of fonts that are clearer for that individual to read. Barriers they may encounter on the Web include:
  • Web pages with absolute font sizes that do not enlarge easily
  • Web pages that are inconsistently laid out and therefore difficult to navigate when enlarged due to loss of surrounding context
  • browsers that do not support user override of authors' style sheets
Color Blindness
Color blindness is a lack of perceptual sensitivity to certain colors. This may result in difficulty distinguishing between red and green, or between yellow and blue. Sometimes it may mean an inability to perceive any color. 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 pattern
  • browsers that do not support user override of authors' style sheets

Hearing Disabilities

Deafness involves a substantial uncorrectable impairment of hearing in both ears. Some deaf individuals' first language is a sign language rather than a spoken and written language. 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 of hearing and may rely on amplification and/or redundant text with audio. Barriers encountered on the Web include:
  • lack of captions or transcripts for audio content on the Web to support comprehension of audio tracks

Visual and Hearing Disabilities

If an individual has substantial uncorrectable losses of vision and hearing, the individual may be considered deaf-blind. Depending on the extent of vision or hearing losses, requirements with regard to Web access may differ from those for vision-related disability alone, or those for hearing-related disability alone. Barriers include:
  • video that is described in audio but not described in text
  • captions that cannot easily be enlarged

Physical Disabilities

Paralysis involves partial or complete loss of muscular control and sensation in part of the body. Paresis involves slight to extensive weakness in part of the body. Either condition may be accompanied by pain which can further impede movement. Individuals with paralysis or paresis may have difficulty using a regular mouse or keyboard. They may use a specialized mouse; they may use a keyboard with a layout of keys that matches their range of motion; they may use 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 not be able to activate commands that require multiple keystrokes simultaneously. They may need longer response times when dealing with interactive forms on Web sites. Barriers they may encounter include:
  • browsers and authoring tools that do not support serialized keystrokes for commands
  • forms that cannot be tabbed through in a logical order
  • interactive forms with time-limited response options
If an individual's muscles are tense and contracted, or if an individual has problems with coordination or involuntary movements, it may affect their ability to select keys on the keyboard or targets on a Web page. They may use similar assistive technologies as individuals with paralysis or paresis; and may need longer response times for interactive forms. Barriers they may encounter include:
  • interactive forms with time-limited response options
If an individual's vocal chords are affected by a physical disability, he or she may have difficulty producing speech that is recognizable by some voice recognition software. As voice recognition is increasingly used in Web-based applications, an individual with a speech disability may need alternatives to a voice-based interface. Barriers they encounter may include:
  • Web sites that require voice-based interaction

Cognitive and Neurological Disabilities

Learning disabilities
Some individuals have difficulty processing written language or images when read visually, or spoken language when heard, or numbers when read visually or heard. Some specific learning disabilities can affect ability to focus. Barriers include:
  • lack of alternative modalities for information on Web sites, for instance audio in addition to visual, or text or visuals in addition to audio
  • lack of clear and consistent organization of Web sites
  • distracting visual or audio elements
Impairments of intelligence
Some individuals learn more slowly or have difficulty understanding complex concepts. Barriers include:
  • lack of clear or consistent organization of Web sites
  • use of overly complex language on Web sites
Memory impairments
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. Barriers include:
  • lack of clear or consistent organization of Web sites
  • use of overly complex language on Web sites
Neurological disabilities
Some individuals with seizure disorders are triggered by visual flickering or audio signals at a certain frequency. 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
Psychiatric disabilities
Individuals with mental or emotional disabilities may have difficulty focusing. Barriers include:
  • lack of clear and consistent organization of a Web sites
  • distracting visual or audio elements

Changes in Ability due to Aging

Changes in multiple abilities at the same time
Aging can bring multiple changes in abilities which can complicate the process of making accommodations to a single disability. Examples include impairments in vision, hearing, memory, or dexterity, any of which can affect an individual's ability to access Web content, however together these conditions can be more complex to accommodate. For example, someone with low vision may need screen magnification, however one loses some surrounding contextual information when using screen magnification, which may further hinder an individual who also has limited short-term memory. Barriers can include any of the issues already mentioned above.

2. Tools

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, plug-ins.

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.
Screen magnifiers
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.
Screen readers:
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.
Sound notification
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.
Scanning software
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
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

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About the Web Accessibility Initiative

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W3C's Web Accessibility Initiative (WAI) addresses accessibility of the Web through five complementary activities that:

  1. Ensure that the technology of the Web supports accessibility
  2. Develop accessibility guidelines
  3. Develop tools to facilitate evaluation and repair of Web sites
  4. Conduct education and outreach
  5. 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 NCR.

Additional information on WAI is available at

About the WAI Web Accessibility Guidelines


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:

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


Gregg Vanderheiden, Kate Vanderheiden, [add EOWG once reviewed, other WAI groups once reviewed]


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