Glossary · Accessibility term
Disability
Disability results from the interaction between a health condition and the world around it. That is the World Health Organization's framing, and it is the one that matters for web work, because it puts the barrier rather than the person at the center of the question. Somebody who is blind is not stopped by blindness on a well-built site. They are stopped by an unnamed button. WHO estimated in March 2023 that 1.3 billion people experience significant disability, about 16% of the world, or one in six. The categories web accessibility has to reach are auditory, cognitive, neurological, physical, speech and visual. Speech is the one that falls off the list soonest, which is how voice-only support lines keep getting built.
In practice
Three kinds of limit run into the same barriers, and one fix often serves all three. Permanent conditions. Temporary ones, like a broken wrist or an eye infection. Situational ones, like bright sunlight on a screen or holding a baby with one arm. Captions carry sound to a deaf viewer and to a commuter with no headphones. Big targets serve a hand tremor and a bumpy train. That is why the audience for this work is wider than a disability statistic suggests, and it is a tendency rather than a rule, since plenty of what a blind reader needs helps nobody in sunlight at all.
The legal definition is a different instrument from the medical one, and in the US it is the one that decides exposure. The ADA defines disability with respect to a person in three prongs. A physical or mental impairment that substantially limits one or more major life activities. A record of such an impairment. Or being regarded as having one. That third prong surprises business owners, and it is narrower than the phrase sounds. It reaches somebody subjected to a prohibited action because of an impairment they have or are thought to have, and it excludes impairments that are both transitory and minor. The tax code imports that same definition for the accessibility credit.
WCAG never defines the word. The standard is built around what content has to do rather than around who is disabled. So its criteria help people the drafters never had in mind, and the standard survives changes in how disability gets defined.
Why it matters
A great many of the 1.3 billion are not using specialist equipment at all. They are using your site with the text turned up, or one hand, or the sound off, or after a day that left them with nothing to spare for concentrating. Treating disability as an ordinary part of your audience rather than an edge case is the shift that makes everything after it straightforward. The question stops being who this is for. It becomes what the page assumes about the person reading it. Every assumption you can name is one you can drop.
The definition that decides US exposure
The ADA's test has three prongs and only the first is the obvious one. An impairment that substantially limits a major life activity. A record of one. Or being regarded as having one, which covers a person with no impairment at all who was treated badly because somebody thought they had, unless the impairment in question is both transitory and minor. Major life activities include seeing, hearing, reading, concentrating, thinking and communicating, so the list reaches most of what a website asks anybody to do.
Where this shows up on the site
Related terms
- AccessibilityAccessibility means building websites and tools so that people with disabilities can use them.
- Assistive technologyAssistive technology is hardware or software that gives a person with a disability more than a mainstream browser offers on its own.
- Inclusive designInclusive design means treating the full range of human variation as the starting point rather than as an edge case to accommodate once the design is finished.
- Universal designUniversal design is the idea that one design should work for as many people as possible without anybody needing a special version or a separate adaptation.
- Vestibular disorderA vestibular disorder is a condition affecting balance and spatial orientation, and it runs through the inner ear and the brain rather than the inner ear alone.
Knowing the word is the easy part.
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