Accessibility Glossary
Plain-English definitions of the digital accessibility terms you'll come across most often — handy whether you're studying for a certification or just getting started.
Accessibility (a11y)
Designing products, content, and services so people with disabilities can perceive, understand, navigate, and interact with them. "a11y" is shorthand — "a", then 11 letters, then "y".
WCAG
The Web Content Accessibility Guidelines — the international standard (from the W3C) that defines how to make web content accessible. Versions include 2.0, 2.1, and 2.2, with conformance levels A, AA, and AAA.
POUR
The four principles behind WCAG: content must be Perceivable, Operable, Understandable, and Robust.
Conformance level (A / AA / AAA)
WCAG's three tiers of requirements. Level A is the minimum, AA is the common legal target (and what most laws reference), and AAA is the most stringent.
Success criterion
An individual, testable WCAG requirement (for example, "1.4.3 Contrast (Minimum)"). Conformance is measured against these criteria.
AODA
The Accessibility for Ontarians with Disabilities Act — Ontario legislation whose Integrated Accessibility Standards Regulation requires accessible websites (WCAG 2.0 AA) and more. See our AODA checklist.
ADA
The Americans with Disabilities Act — US civil-rights law increasingly applied to websites and digital services.
Section 508
US federal law requiring electronic and information technology used by federal agencies to be accessible; it references WCAG.
EN 301 549
The European accessibility standard for ICT products and services, which incorporates WCAG.
PDF/UA
"PDF/Universal Accessibility" (ISO 14289) — the standard for accessible PDF documents. See our PDF checklist.
ARIA
Accessible Rich Internet Applications — a set of HTML attributes (roles, states, properties) that make dynamic and custom components understandable to assistive technology. Use it to fill gaps, not to replace semantic HTML.
Semantic HTML
Using HTML elements for their real meaning (buttons, headings, lists, landmarks) rather than generic <div>s. It gives assistive technology built-in structure.
Assistive technology (AT)
Hardware or software that helps people with disabilities use digital content — screen readers, screen magnifiers, switch devices, voice control, and more.
Screen reader
Software that reads page content aloud (or sends it to a Braille display) for blind and low-vision users. Common examples: NVDA, JAWS, VoiceOver.
Focus indicator
The visible outline showing which element currently has keyboard focus. It must be clearly visible so keyboard users can see where they are.
Alt text
A short text description of a meaningful image, read aloud by screen readers. Decorative images use empty alt (alt="") so they're skipped. Try our alt-text checker.
Colour contrast
The brightness difference between text and its background. WCAG AA requires at least 4.5:1 for normal text. Check yours with our contrast checker.
Landmark
A region of a page (header, nav, main, footer) that assistive technology can jump between, defined with semantic elements or ARIA roles.
Heading structure
The hierarchy of headings (h1–h6) that lets users understand and navigate a page. One h1 per page, no skipped levels.
Reading order
The sequence in which content is announced by assistive technology. It must match the logical visual order, especially in PDFs and complex layouts.
Tagged PDF
A PDF with an underlying structure of tags (headings, paragraphs, tables, lists) that assistive technology uses to read it. Untagged PDFs are inaccessible.
Captions
Synchronised text for the audio in a video, including speech and important sounds — essential for Deaf and hard-of-hearing users.
Transcript
A full text version of audio (or audio-visual) content, useful for people who can't hear it and for search engines.
Audio description
Narration added to a video that describes important visual information for blind and low-vision users.
Skip link
A link (often the first focusable item) that lets keyboard users jump straight to the main content, past repeated navigation.
Universal design
Designing for the widest range of people from the start, so fewer separate accommodations are needed. Accessibility is part of universal design.
Remediation
Fixing existing accessibility barriers in a website or document. See our remediation service.
VPAT
Voluntary Product Accessibility Template — a document vendors use to report how a product meets accessibility standards; often requested in procurement.
Plain language
Clear, simple writing that more people can understand, including those with cognitive or learning disabilities.
CPACC / WAS / CPWA
IAAP certifications: CPACC (foundational), WAS (technical web), and CPWA (the combined credential). See our comparison guide.