Accessibility terminology gets thrown around a lot, often without much explanation, so here’s a working reference for the terms that actually come up when you’re evaluating a compliance standard, an audit report, or a vendor’s product page. Terms are grouped loosely by theme rather than strict alphabetical order, since a few of them only make sense in relation to each other.

WCAG (Web Content Accessibility Guidelines): The internationally recognized technical standard for web accessibility, published by the W3C. Nearly every other standard and law on this list ultimately points back to WCAG as its technical baseline. Current versions in active use are 2.1 and 2.2, each with conformance levels A, AA and AAA (AA is the level almost every law and standard actually requires).

POUR: The four principles WCAG is organized around: content must be Perceivable, Operable, Understandable and Robust. If a fix doesn’t map to one of these four, it’s probably not actually an accessibility fix.

ADA (Americans with Disabilities Act): U.S. civil rights law. Courts and the Department of Justice have applied Title III of the ADA to private-sector websites and Title II to state and local government sites, generally referencing WCAG 2.1 AA as the practical standard even though the ADA itself doesn’t name a specific technical standard.

Section 508: A U.S. federal law requiring federal agencies, and vendors selling to them, to make electronic and information technology accessible. Since a 2017 update, its technical requirements point directly to WCAG 2.0 A and AA.

EAA (European Accessibility Act): An EU directive requiring a wide range of products and services sold to EU consumers to be accessible. Enforcement began June 28, 2025 for new products and services, with later transition deadlines for existing contracts and products already in use.

EN 301 549: The harmonized European technical standard that defines what “accessible” means for EAA compliance purposes. It incorporates WCAG 2.1 AA in full as of version 3.2.1, so conforming to WCAG 2.1 AA covers most of its web content requirements.

PDF/UA: A technical standard specifically for accessible PDF documents (tagged reading order, structured headings, proper alt text within the PDF itself), separate from but related to WCAG.

Documentation and testing

VPAT (Voluntary Product Accessibility Template): A standardized document a vendor fills out describing how well a specific product conforms to WCAG, Section 508 and EN 301 549, criterion by criterion. Commonly requested during enterprise and government procurement. The completed document is sometimes called an ACR (Accessibility Conformance Report).

Accessibility statement: A public page explaining an organization’s accessibility commitment, current conformance status, and how to report barriers. Often required for EU public-sector sites under the Web Accessibility Directive, and commonly published voluntarily elsewhere as documentation of a good-faith effort.

Automated scan: A tool that crawls a site’s code and flags likely WCAG issues automatically, without human judgment. Useful for catching a meaningful subset of problems quickly, but it can’t evaluate everything a real conformance claim requires, since some success criteria genuinely need a human to judge.

Manual audit: A human expert testing a site directly, often including real assistive-technology testing (screen readers, keyboard-only navigation), to catch what automated scanning alone misses. Vendors like Deque Systems specialize in this kind of expert-led testing work.

Assistive technology (AT): Any tool a person uses to interact with digital content differently than the default, most commonly a screen reader, but also including screen magnifiers, switch devices, voice control software and braille displays.

Interface and content terms

Screen reader: Software that reads a page’s content aloud or outputs it to a braille display, used primarily by blind and low-vision users. Common examples include NVDA and JAWS on Windows, VoiceOver on Apple devices, and TalkBack on Android.

Alt text (alternative text): A short text description attached to an image, read aloud by a screen reader in place of the image itself. Should describe what the image actually conveys, not every visual detail, and purely decorative images should have empty alt text so screen readers skip them.

Focus order: The sequence in which interactive elements (links, buttons, form fields) receive keyboard focus when a user presses Tab. Should follow a logical reading order matching the visual layout; a mismatched focus order is a common and confusing barrier for keyboard-only users.

ARIA (Accessible Rich Internet Applications): A set of HTML attributes that describe custom interactive components to assistive technology when native HTML doesn’t have a built-in element for them. Best used to fill genuine gaps rather than as a default add-on, since incorrect ARIA can make a page harder to use than no ARIA at all.

Semantic HTML: Writing HTML using elements that describe what content actually is (<button>, <nav>, <h1>) rather than generic elements styled to look the part. Semantic HTML gives assistive technology a real structure to work with automatically, without needing extra ARIA to compensate.

Color contrast: The difference in luminance between text and its background, measured as a ratio. WCAG AA requires a minimum ratio (generally 4.5:1 for normal text) so people with low vision or color vision differences can read it. Low contrast text is consistently the single most common WCAG failure found across the web; the 2026 WebAIM Million study found it on 83.9% of home pages.

Keyboard navigation: The ability to operate every interactive part of a site (menus, forms, buttons, modals) using only a keyboard, with no mouse. Essential for many screen reader users and for people with motor impairments who can’t use a mouse.

Vendor and product terms

Accessibility widget / overlay: A script-based tool, usually a single line of JavaScript, that adds an on-page adjustment panel (contrast, font size, reading aids) and, in many cases, some automated remediation like alt text generation. Companies like Wawsome, UserWay and accessiBe sell products in this category, often paired with monitoring or manual review add-ons.

Overlay controversy: The ongoing, well-documented debate over how effective widget-based automated remediation actually is. Surveys of accessibility practitioners have found significant skepticism about overlays specifically, which is part of why several vendors in the category now pair automation with genuine manual audit work rather than selling automation alone.

A few more terms worth knowing

Conformance level: WCAG defines three levels, A, AA and AAA, each stricter than the last. AA is the level virtually every law and standard actually requires; AAA is a higher bar that most sites don’t attempt in full, since some AAA criteria are genuinely difficult to meet for certain kinds of content.

Accessible name: The text a screen reader announces for an interactive element, like a button or link. It might come from the element’s visible text, an aria-label attribute, or an associated <label> element for a form field. Two elements can look identical but have very different, or missing, accessible names.

Landmark: A region of a page marked with a semantic role, like <nav>, <main> or <footer>, that lets a screen reader user jump directly to that section instead of reading through everything above it first. Well-placed landmarks are one of the simplest ways to make a page faster to navigate for a screen reader user.

Skip link: A link, usually the very first focusable element on a page and often visually hidden until it receives keyboard focus, that lets a keyboard user jump straight to the main content and skip repeated navigation menus. A missing skip link forces a keyboard-only visitor to tab through the entire header on every single page.

Demand letter: A letter, typically from a law firm, alleging that a website violates accessibility law (most often the ADA in the U.S.) and requesting remediation, sometimes alongside a monetary demand, often as a precursor to a lawsuit if it goes unaddressed.

Remediation: The actual work of fixing an identified accessibility issue, whether that’s a code change, a content edit (like adding real alt text), or a design adjustment. Distinct from an audit, which identifies issues, and from a widget’s automated adjustments, which may address some issues without touching the underlying code.