The vocabulary, without the specification voice.
31 terms you will meet in an audit report, a vendor's VPAT or a procurement review — defined for someone who has to make a decision, not for a standards editor. Every term has its own anchor, so you can link straight to one.
A
ADA Title II
The part of the Americans with Disabilities Act covering state and local government. The DOJ's 2024 web rule names WCAG 2.1 Level AA specifically, with compliance dates of April 2026 for entities serving 50,000 or more and April 2027 for everyone else.
ADA Title III
The part covering places of public accommodation — most private businesses serving the public. No codified web standard, which is why litigation drives practice here, with courts and settlements repeatedly using WCAG Level AA as the measure.
ACR Accessibility Conformance Report
The document a completed VPAT produces. In a contract it is a representation about the product, which is why an honest one with dated gaps is worth more than one claiming universal support.
Assistive technology
Software or hardware someone uses to access content: screen readers, screen magnifiers, speech input, switch access, braille displays. Testing with it is the part automated tools cannot replace.
Accessible name
The label assistive technology announces for a control. It comes from the visible text, or an aria-label, or an associated label element. A button with no accessible name announces as just "button", which tells the user nothing.
ARIA Accessible Rich Internet Applications
A set of HTML attributes that describe roles, states and properties to assistive technology. Useful for custom components, and easy to get wrong — incorrect ARIA is generally worse than none, because it overrides what the browser would have reported.
Alt text
The text alternative for an image, serving the same purpose the image serves. A decorative image takes an empty alt attribute so it can be skipped deliberately — a missing attribute is an omission, an empty one is a decision.
Audio description
A narration track describing visual information a video's audio does not convey. Distinct from captions: captions serve deaf users, audio description serves blind users, and they are separate obligations.
Accessibility overlay
A third-party script that claims to make a site conformant automatically. It cannot: automated repair reaches only the subset a scanner can detect, much of the disability community rejects these products, and they have been named in accessibility litigation.
Accessibility statement
A published page naming the standard you work to, what has been tested, known limitations, and how to report a barrier. One claiming perfection with no limitations should be read sceptically — it is a public claim you can be measured against.
C
Conformance claim
A statement that defined content meets a specific WCAG version and level at a point in time, supported by testing evidence. This is what exists instead of certification — there is no accrediting body and no permanent status.
Contrast ratio
The measured difference in luminance between text and its background. Level AA requires 4.5:1 for body text and 3:1 for large text and interface components. Low contrast is the single most common failure on the web.
Captions
Synchronised text for the audio in a video, including speaker identification and meaningful non-speech sound. Auto-generated captions are a starting point, not a result: they reliably mangle names, jargon and numbers.
E
EN 301 549
The European accessibility standard, used to demonstrate conformance with the European Accessibility Act. It incorporates WCAG Level AA and adds requirements for hardware, software and support services.
European Accessibility Act
EU legislation in application since June 2025, covering products and services sold into the EU — e-commerce, consumer banking, e-books, ticketing and transport among them. It applies based on where you sell, not where you are incorporated.
F
Focus order
The sequence in which keyboard focus moves through a page. It should follow the visual reading order. Positive tabindex values and CSS reordering are the usual causes when it does not.
K
Keyboard trap
A component keyboard focus can enter but not leave. One of the few failures that can strand someone completely — modal dialogs and embedded media players are the usual culprits.
L
Level AA
The conformance level regulators, courts and procurement teams actually use. Meeting it means satisfying every Level A and every Level AA success criterion — conformance is pass/fail per criterion, not a percentage.
Level AAA
The highest conformance level. W3C does not recommend it as a general policy target because some criteria cannot be satisfied for all content, and no major regulation cites it. Treat a vendor promising AAA sitewide with caution.
Landmark
A region of a page exposed to assistive technology, such as main, navigation or contentinfo. Landmarks let a screen reader user jump straight to the content instead of traversing the header on every page.
R
Reflow
The requirement that content adapt to a 320 pixel wide viewport without scrolling in two directions. Narrow your browser and see — fixed widths, wide tables and long unbreakable strings are what break it.
Remediation
The work of fixing identified accessibility defects. Done well it happens at the component level, where one fix clears every instance, rather than page by page.
S
Success criterion
A single testable requirement in WCAG, identified by a number like 1.4.3. Findings should always cite one — it turns an opinion into something checkable against the standard.
Section 508
The US federal procurement rule requiring accessible technology, incorporating WCAG Level AA by reference. Most organisations meet it as sellers rather than buyers — it is what makes a customer ask for your VPAT.
Section 504
The Rehabilitation Act provision reaching recipients of federal financial assistance — schools, universities, many nonprofits and health programmes. Often the hook for accessibility obligations at organisations that are not government bodies.
Screen reader
Software that converts on-screen content to speech or braille. The common ones are JAWS and NVDA on Windows, VoiceOver on Apple devices, and TalkBack on Android. Implementations differ, so a serious audit tests more than one.
Skip link
A link, usually first in the page and visible on focus, that jumps past repeated navigation to the main content. Without one a keyboard user tabs through every header link on every page.
T
Target size
How large an interactive control is. WCAG 2.2 requires at least 24 by 24 CSS pixels, or enough spacing to reach that effective size. Dense icon rows and cramped mobile pagination are the usual failures.
Tagged PDF
A PDF containing a structure tree — headings, lists, tables, reading order — that assistive technology can follow. A scanned document with no text layer is not tagged and is completely inaccessible.
V
VPAT Voluntary Product Accessibility Template
The form a vendor fills in to describe how their product measures against an accessibility standard. Completed, it produces an Accessibility Conformance Report. Nobody audits these, so read the remarks column rather than the ratings.
W
WCAG Web Content Accessibility Guidelines
The technical standard nearly every accessibility regulation points at, published by the W3C. Organised into four principles and three conformance levels. When a rule says a site must be accessible, WCAG is almost always how that gets measured.
Knowing the words is not the same as knowing where you stand.
If you are reading this because a report, a VPAT or an RFP used language you did not recognise, the fastest way to turn that into something concrete is to run the checks against your own pages and see what comes back.
Check Your Own Pages