Computer accessibility

In human-computer interaction, computer accessibility refers to the usability of a computer system by people with disabilities. It is largely a software concern. However, when hardware or software is used to customize a computer for a disabled person, that equipment is known as adaptive technology.

There are several types of disabilities that impact computer use:

Designing with accessibility in mind can often enhance usability for all users and for automated access to the site, such as by search engines. A key to accessibility is to let people access content in their preferred way. This can benefit fully able users as well as those with disabilities: for example, some people may prefer icons and others may prefer text; even fully able people may want to adjust text sizes depending on their viewing circumstances; search engines, like blind people, generally cannot make much use of graphics.

Different sites will require different degrees of concern for accessibility. For example: a site providing information specific to ADHD would have a lot more need to be easily accessible by people with ADHD than would a site about atomic physics; a government site of general interest or a resource directory for people in crisis would need to take into account as many disabilities as possible, whereas a site selling spectacles probably would have no reason to make itself easily accessible to the totally blind.

Many people with visual impairments or dyslexia will want to change the colours of text or the background to make it easier to read. Many people with dyslexia or ADHD will want to stop moving images on the screen whilst they are reading, as they are easily distracted. People with ADHD may also be confused or distracted by link-rich sites: they can have difficulty when presented with so many options.

Accessibility is strongly related to universal design in that it is about making things as accessible as possible to as wide a group of people as possible. However, products marketed as having benefited from a Universal Design process are often actually the same devices customized specifically for use by people with disabilities. It is rare to find a Universally Designed product at the mass-market level that is used mostly by nondisabled people; Oxo Good Grips housewares are continually held up as an example.


Considerations for specific disabilities

Cognitive disabilities and illiteracy

The biggest challenge in computer accessibility is to make resources accessible to people with cognitive disabilities — particularly those with poor communication skills — and those without reading skills. For starters, site designers should ensure that navigation and content is as plain and simple as appropriate is a useful start; long texts should provide summaries. Texts can be supplemented by symbols, illustrations, comics and photographs. Screen readers are of only limited use, due to the differences between spoken and written language and the complexity of text. A set of guidelines [1] ( and two accessible[2] ( web portals designed for people developing reading skills are [3] ( — try typing a letter with your keyboard for more — and [4] ( with enhanced graphics, unique style controls and improved interactivity (requires SVG supported browser).

Visual disabilities

Another significant challenge in computer accessibility is to make software usable for people with visual impairment since computers are largely visual devices. For people with poor vision, it is helpful to use large fonts, high-contrast icons etc. supplemented with auditory feedback and screen magnifying software. In the case of blindness, text to speech (screen reader) software is essential.

About 8% of people, mostly males, suffer from some form of colorblindness. In a well-designed user interface, color should not be the only way of distinguishing between different pieces of information. However, the only colours that matter are colours that people with a deficiency might confuse, which generally means red and green and blue and green.

Motor disabilities

Some people may not be able to use a conventional input device, such as the mouse or the keyboard. Therefore it is important for software functions to be accessible using both or either device; ideally, software uses a generic API that permits the use even of highly specialized devices unheard of at the time of software development. Keyboard shortcuts and mouse gestures are ways to achieve this. More specialized solutions like on-screen keyboards and alternate input devices like joysticks and trackballs are also available.

The astrophysicist Stephen Hawking is a famous example of a person suffering from motor disability. He uses special software that allows him to control his computer using his remaining small movement ability. His computer also talks for him.

Aural disability

While sound user interfaces have a secondary role in common desktop computing, usually limited to system sounds as feedback, software producers take into account people who can't hear, either for personal disability, noisy environments, silence requirements or lack of sound hardware. The system sounds like beeps can be substituted or supplemented with flashing parts of the screen or text (akin to close captions).

Web and accessiblity

See also: web accessibility.

Standards and guidelines

On the World Wide Web, the W3C has produced specific guidelines for accessibility via the Web Accessibility Initiative (WAI).

The Cascading Style Sheets system has been devised with this in mind, since it gives the reader full control over the appearance of the page.


In the United States, since 1998, under Section 508 (29 U.S.C. ‘ 794d) (of Rehabilitation Act), (Federal) agencies must give disabled employees and members of the public access to information that is comparable to the access available to others. | Section 508 Related Information (

Examples of considerations

Most web browsers have an option to ignore the font size specified in a webpage, so that the user can circumvent a small font forced upon him or her by a webpage author. However, sometimes a webpage author fails to take into account that users may want to apply such an option and designs a webpage such that applying this option gives poor results, such as too small a distance between lines, disabled scrolling even though texts do not fit in assigned spaces, overlapping texts, etc.

See also: modding.

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