Glossary · Accessibility term
Accessibility supported
A way of using a technology is accessibility supported when two things are true together. First, that way of using it has been tested for interoperability with the assistive technology people actually have, in the human languages the content is written in. Second, there is an accessibility-supported user agent people can get hold of, which means either widely distributed software, or a widely distributed plug-in, or a closed environment like a corporate network where the required software is supported, or a user agent available to download or buy that costs a disabled person no more than anybody else and is no harder for them to find and obtain. Something can be valid, documented and specification-correct and still fail both halves.
In practice
Test with the software people actually use rather than trusting the specification. Where you cannot test everything, and almost nobody can, you are allowed to lean on published compilations of what assistive technology supports what. Nobody has to use one, anybody may publish one, and a customer buying from you may name the one they want used.
WCAG will not tell you how much support is enough. It defines what support means and then hands the threshold to whoever is setting the requirement, which is you, your customer or your regulator. So if a pattern works in one browser with one screen reader and nowhere else, calling it unsupported for your audience is your judgement to make and a defensible one, and it is not a line the standard drew.
Support is a fact about the software people are running, not about the standard, and it is a fact about single uses rather than whole technologies. Even HTML lacks support for at least one feature, so asking whether a technology is accessibility supported is a question with no answer. Ask it about the way you are using the thing.
Why it matters
It is the requirement that stops conformance being a paper exercise. Valid, documented, specification-correct markup that no assistive technology honours has not helped anybody. It is also not a ban on using unsupported technology. You may use one as long as you do not rely on it, and the requirement names both halves of what has to survive. Any information and any functionality provided in an unsupported way has to be available another way that is supported. Preserving the words while losing the transaction does not meet it. The unsupported part must not interfere with the rest of the page either.
Correct and useless
Several ARIA roles are in the specification and poorly supported in practice. Using one and stopping there is technically defensible and functionally nothing. The last of the four availability routes has a money side people miss. Where support rests on somebody downloading or buying a user agent rather than on software they already have, that user agent has to cost a disabled person no more than it costs anybody else, and be no harder for them to get hold of.
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