Web Accessibility Glossary

WCAG 2.1 Level AA

The Web Content Accessibility Guidelines (WCAG) 2.1 Level AA is the internationally recognized standard for web accessibility published by the World Wide Web Consortium (W3C). It includes 50 specific success criteria organized under four principles: Perceivable, Operable, Understandable, and Robust. It's the benchmark referenced by the U.S. Department of Justice and federal courts for ADA compliance.

POUR Principles

The four fundamental principles organizing WCAG 2.1 success criteria:

• Perceivable: Information must be presentable to users' senses
• Operable: Users must be able to navigate and use functionality
• Understandable: Information and operation must be clear
• Robust: Content must work with assistive technologies

Success Criteria

Specific, testable requirements within WCAG 2.1. Each criterion is identified by a number (e.g., 1.1.1, 2.4.3) and describes what must be accomplished for accessibility compliance.

ADA (Americans with Disabilities Act)

Federal civil rights law prohibiting discrimination against people with disabilities. Title III applies to websites operated by businesses and requires accessibility for people with disabilities, though specific technical standards are not defined in the law itself.

Screen Readers

Software that converts digital text into speech or refreshable Braille displays, allowing blind and visually impaired users to navigate websites. Popular screen readers include JAWS (Job Access With Speech), NVDA (NonVisual Desktop Access), and VoiceOver (built into Apple devices). They rely on proper HTML structure, ARIA attributes, and alt text to understand page content.

Assistive Technology

Software or hardware used by people with disabilities to access websites, including screen readers, magnification software, speech recognition, keyboard-only navigation, and alternative input devices.

JAWS (Job Access With Speech)

The most widely used commercial screen reader for Windows computers. Often the testing standard for professional accessibility audits.

NVDA (NonVisual Desktop Access)

A free, open-source screen reader for Windows. Widely used for accessibility testing and by users who need screen reading capabilities.

VoiceOver

Apple's built-in screen reader for macOS and iOS devices. Activated via keyboard shortcuts or accessibility settings.

Alt Text (Alternative Text)

A short description added to images on a website. When a blind person uses a screen reader, the alt text is read aloud so they understand what the image shows. Alt text is required for all non-decorative images under WCAG 2.1 Level AA (Success Criterion 1.1.1).

ARIA (Accessible Rich Internet Applications)

A set of attributes used to enhance semantic meaning for assistive technologies. Common ARIA implementations include:

• aria-label: Provides an accessible name for elements
• aria-labelledby: Links an element to another element that provides its label
• aria-describedby: Associates an element with additional description
• aria-live: Announces dynamic content updates

Semantic HTML

Using appropriate HTML elements based on their intended purpose (<button> for buttons, <nav> for navigation, <h1> for headings, etc.) rather than generic elements like <div> with CSS styling. Critical for screen reader compatibility.

Landmark Regions

Semantic HTML elements that identify major page sections (<nav>, <main>, <header>, <footer>, etc.), enabling screen reader users to navigate by landmarks and understand page structure.

Form Labels

Text descriptions that identify what information belongs in each form field. Labels must be programmatically associated with their form inputs using the <label> element with matching for/id attributes. Required by WCAG 2.1 Level AA (Success Criteria 1.3.1, 3.3.2, 4.1.2).

Heading Hierarchy

The proper sequential ordering of HTML heading levels (h1, h2, h3, etc.). Breaking the hierarchy (e.g., jumping from h1 directly to h3) prevents screen reader users from properly navigating page structure.

Color Contrast

The difference between text and background colors. WCAG 2.1 Level AA requires a minimum 4.5:1 contrast ratio for normal text and 3:1 for large text. Low contrast affects people with low vision and color blindness.

Focus (Focus Indicator)

The visual indicator showing which element is currently selected when navigating with a keyboard. Users need visible focus indicators to know where they are on a page. Required by WCAG Success Criterion 2.4.7 (Focus Visible).

WebAIM Contrast Checker

A free online tool for testing color contrast ratios to ensure they meet WCAG requirements.

Keyboard Navigation

The ability to interact with a website using only keyboard keys (Tab, Enter, Arrow keys, Escape, etc.) without a mouse. Essential for people with motor disabilities and blind users who navigate by keyboard and screen reader. Governed by WCAG Success Criteria 2.1.1 (Keyboard), 2.1.2 (No Keyboard Trap), 2.4.3 (Focus Order), and 2.4.7 (Focus Visible).

Tab Order

The sequence in which keyboard Tab navigation moves through interactive elements on a page. Should follow a logical, left-to-right, top-to-bottom order.

Keyboard Trap

A situation where keyboard users cannot navigate away from an element using only the keyboard. For example, a modal dialog that traps focus with no escape method. Violates WCAG Success Criterion 2.1.2.

Empty Links

Clickable elements with no text that screen readers can announce. Commonly occur with icon-only links (shopping cart, social media icons, hamburger menus) where blind users hear only 'link' without knowing where it goes. Violates WCAG Success Criterion 2.4.4 (Link Purpose in Context).

Accessible Names

Text that identifies the purpose of interface components. Required by WCAG 2.1 Level AA Success Criterion 4.1.2 (Name, Role, Value). Can be provided via visible text, alt text, aria-label, or aria-labelledby.

Video Captions

Synchronized text displayed on videos showing spoken dialogue, sound effects, speaker identification, and other audio information. Required for deaf and hard-of-hearing users, non-native speakers, and people in noisy environments. WCAG 2.1 Level AA (Success Criterion 1.2.2) requires captions for all prerecorded videos.

Closed Captions (CC)

Synchronized text that includes all dialogue and relevant sound effects (as opposed to subtitles which typically show only dialogue).

WebVTT (.vtt)

A file format for creating text tracks for HTML5 videos. Contains caption text with synchronized timestamps.