Accessibility Glossary

Broaden your vocabulary

Understanding digital accessibility starts with learning the language. Below is a reference glossary of the most important terms used in accessibility standards, assistive technology, and compliance work.

A11y

A numeronym for “accessibility” — the “a”, 11 letters, then “y”. Widely used in the accessibility community as shorthand.

ADA

The Americans with Disabilities Act. US legislation that prohibits discrimination against people with disabilities, including in digital contexts. Web accessibility lawsuits are frequently filed under the ADA.

Alt Text

A written description of an image, added to the HTML alt attribute. Screen readers read alt text aloud so users who cannot see images still understand the content.

AODA

Accessibility for Ontarians with Disabilities Act. Canadian provincial legislation that sets accessibility standards for organizations operating in Ontario.

AOM

Accessibility Object Model. A browser API that exposes the accessibility tree to JavaScript, allowing developers to query and modify accessibility properties programmatically.

API

Application Programming Interface. In the accessibility context, APIs — including platform accessibility APIs — are used by assistive technologies to communicate with software and retrieve information about UI elements.

ARIA

Accessible Rich Internet Applications. A set of HTML attributes (prefixed with aria-) that communicate the role, state, and properties of UI elements to assistive technologies when native HTML semantics are insufficient.

Assistive Technologies (AT)

Hardware or software that helps people with disabilities use computers and the web. Examples include screen readers, screen magnifiers, switch access devices, voice input software, and refreshable Braille displays.

CAPTCHA

Completely Automated Public Turing test to tell Computers and Humans Apart. CAPTCHAs present a barrier for many users with disabilities. Accessible alternatives include audio CAPTCHAs or logic-based challenges.

Color Contrast

The difference in luminance between foreground text and its background. WCAG requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text to ensure readability for users with low vision.

DOM

Document Object Model. The browser’s structured representation of an HTML page. Assistive technologies use the DOM — and the accessibility tree derived from it — to understand and interact with page content.

EAA

European Accessibility Act. EU Directive 2019/882, which requires products and services — including websites and mobile apps — to meet accessibility standards. Enforcement began in June 2025.

Focus Indicator

A visible outline or highlight that shows which element on a page currently has keyboard focus. WCAG requires focus indicators to be visible so keyboard-only users can track their position on the page.

Focus Order

The sequence in which keyboard focus moves through interactive elements on a page. A logical focus order follows the visual layout and the meaning of the content, ensuring keyboard navigation makes sense.

Keyboard Navigation

The ability to navigate and interact with a website using only a keyboard (typically Tab, Shift+Tab, arrow keys, Enter, and Space). Essential for users who cannot use a mouse due to motor disabilities.

Manual Testing

Accessibility evaluation performed by a human tester using assistive technologies and expert judgment. Manual testing catches issues that automated tools cannot detect, such as logical reading order and meaningful link text.

Real Text

Text rendered as HTML characters rather than embedded in an image. Real text can be resized, reflowed, and read by assistive technologies. Images of text fail WCAG success criteria except in logos and decorative cases.

Screen Reader

Software that converts on-screen content — text, images, form elements, and interface controls — into speech or Braille output. Common screen readers include JAWS, NVDA, VoiceOver, and TalkBack.

Section 508

A section of the US Rehabilitation Act that requires federal agencies and federally funded organizations to make their electronic and information technology accessible to people with disabilities.

Semantic HTML

HTML written with elements that convey meaning — such as <nav>, <main>, <article>, <button>, and heading tags (<h1>–<h6>) — rather than using generic <div> and <span> elements for everything. Semantic HTML helps assistive technologies interpret content correctly.

Universal Design

A design philosophy that creates products and environments usable by all people, to the greatest extent possible, without the need for adaptation. In digital contexts, it means building accessible experiences from the start rather than retrofitting them.

VPAT®

Voluntary Product Accessibility Template. A document that describes how a product or service meets the accessibility standards defined in Section 508, WCAG, and other frameworks. Often required by enterprise and government procurement.

W3C

World Wide Web Consortium. The international standards organization that publishes the Web Content Accessibility Guidelines (WCAG) and other web standards.

WCAG

Web Content Accessibility Guidelines. Published by the W3C, WCAG defines how to make web content more accessible. The current version is WCAG 2.2. Success criteria are organized under four principles: Perceivable, Operable, Understandable, and Robust (POUR).