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.

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.

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.

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.

Accessible name

The name assistive technology announces for an element such as a button, link or form field. It comes from visible text, a label, alt text or ARIA attributes.

Decorative image

An image that adds no information, such as a divider line or a background flourish. It gets empty alt text (alt="") so screen readers skip it.

Contrast ratio

A number from 1:1 (no difference) to 21:1 (black on white) that compares how light two colours are. WCAG uses it to measure text and interface contrast.

Focus order

The order in which links, buttons and fields receive focus when someone presses Tab. It should follow the meaning and visual flow of the page.

Reflow

Content that fits a narrow width, equal to 320 CSS pixels, without scrolling in two directions. It lets people zoom to 400% and still read line by line.

Target size

The size of the area you tap or click. WCAG 2.2 asks for targets of at least 24 by 24 CSS pixels at Level AA, with some exceptions.

Live region

A part of a page marked so screen readers announce changes to it without moving focus, such as "3 results found". It is set with aria-live or roles like status.

Braille display

A device with rows of small pins that rise and fall to form Braille characters, showing the text a screen reader is reading. Also called a refreshable Braille display.

Hearing loop

A system that sends sound from a microphone straight to hearing aids and cochlear implants set to the telecoil (T) setting, cutting out background noise.

Text-to-speech

Software that reads digital text aloud. Unlike a screen reader, it usually reads only the content, not the menus and controls. Many people with dyslexia use it.

Wayfinding

How people find their way through a building or a website, using signs, maps, landmarks, sound and touch. Good wayfinding works for people who can't see, hear or remember well.

Tactile graphics

Raised-line versions of maps, diagrams and charts that people who are blind read by touch, usually with Braille labels.

Ableism

Discrimination or prejudice against disabled people, including the assumption that non-disabled ways of doing things are the normal ones.

Web Accessibility Initiative (WAI)

The part of the W3C that develops WCAG, ARIA and other accessibility standards, and publishes free guidance and tutorials.

Duty to accommodate

The legal duty of employers, service providers and landlords in Canada to meet disability-related needs, up to the point of undue hardship.

Artifact (in a PDF)

Content in a tagged PDF that assistive technology should skip, such as page numbers, running headers and decorative lines. It is marked as an artifact instead of being tagged.

Accessible formats

Other versions of information for people who cannot use the original, such as large print, Braille, audio, an accessible digital file or plain language.

Accessibility tree

A simplified version of a page that the browser builds from the code and passes to assistive technology: each element's role, name, state and value.

Inclusive design

A design approach that involves people with a wide range of abilities and situations, so products work for more people. It starts by asking who is being left out.

Accessibility maturity model

A framework for measuring how well an organization builds accessibility into its everyday work, such as policy, buying, training and testing.

Reduced motion

A setting in phones and computers that asks apps and websites to cut down on animation. Websites can respect it with the prefers-reduced-motion media query.