Web Accessibility Glossary
Clear, searchable definitions of accessibility terms based on industry standards. Built and maintained by WebAbility.
A
A11Y
Numeronym for accessibility, representing the 11 letters between A and Y.
Accessibility Audit
A systematic evaluation—manual and automated—of digital experiences against standards such as WCAG, ADA, AODA, or Section 508.
Accessibility Conformance Report (ACR)
A formal document summarizing a product’s accessibility conformance, commonly based on a completed VPAT.
Accessibility Statement
A public statement describing an organization’s commitment to digital accessibility, scope, known gaps, and contact path for assistance.
Accessibility Testing
Methods to verify accessibility including automated scans, manual reviews, and user testing with assistive technologies.
Accessible Authentication
Authentication flows that avoid cognitive function tests such as solving puzzles or memorizing passwords, and provide alternatives like copy/paste and password managers.
Accessible Description
Supplemental help text associated with an element, often via aria-describedby, that provides additional guidance beyond the accessible name.
Accessible Name
The computed name exposed to assistive technologies for an element, derived from label, aria-label, aria-labelledby, or text content.
Accordion
A disclosure pattern made of headers that expand or collapse content. Must be keyboard operable with correct ARIA roles and states.
Active Cursor Indicator
A visible caret or pointer state that helps users track input focus or text insertion position, essential for low-vision and cognitive accessibility.
ADA (Americans with Disabilities Act)
U.S. civil rights law prohibiting discrimination based on disability. Covers public accommodations, employment, and digital accessibility.
ADA Title II
Covers state and local government services, including websites and digital services provided by public entities.
ADA Title III
Covers places of public accommodation and commercial facilities, increasingly applied to websites and mobile apps.
ADHD (Attention Deficit Hyperactivity Disorder)
A neurodevelopmental condition affecting attention, hyperactivity, and impulse control. Interfaces benefit from clear focus management and minimal distractions.
Alt Text (Alternative Text)
Text alternative for images that conveys purpose or meaning when the image cannot be perceived. Decorative images should have empty alt ("").
AODA (Accessibility for Ontarians with Disabilities Act)
Ontario, Canada legislation requiring accessibility compliance for organizations, including WCAG 2.0 Level AA for websites.
Aphasia
A language disorder affecting ability to communicate. Designs benefit from multiple communication modes and clear visual cues.
Application Role
ARIA role indicating custom widgets that require specific keyboard interaction patterns, bypassing standard browser navigation.
ARIA (Accessible Rich Internet Applications)
A specification that defines roles, states, and properties to improve accessibility of complex UI when native semantics are insufficient.
ARIA Live Region
An area of the page that notifies assistive technologies about dynamic updates. Use sparingly with polite or assertive announcements.
Aria-describedby
ARIA attribute that references elements providing additional description for an interactive element.
Aria-expanded
ARIA state indicating whether a collapsible element is currently expanded (true) or collapsed (false).
Aria-hidden
ARIA attribute that hides decorative content from assistive technologies while keeping it visually present.
Aria-label
ARIA attribute providing an accessible name when visible text is insufficient or unavailable.
Aria-labelledby
ARIA attribute that references other elements to compose an accessible name.
Aria-live
ARIA attribute indicating dynamic content that should be announced by assistive technologies. Values: off, polite, assertive.
Assistive Technology (AT)
Software or hardware that helps people with disabilities use digital products, e.g., screen readers, magnifiers, switch devices, voice input.
Audiodescription
Narration track that describes important visual details in video for blind or low-vision users; can be pre‑recorded or via extended description.
Autism Spectrum Disorder (ASD)
Neurodevelopmental condition affecting social communication and behavior. Benefits from predictable interfaces and sensory considerations.
Axe (Accessibility Testing Tool)
Popular automated accessibility testing engine by Deque Systems, available as browser extension and programmatic API.
B
Banner Role
ARIA landmark role for site-oriented content, typically containing site title, logo, and main navigation.
Braille
A tactile writing system for blind or low-vision users, represented with raised dots and supported by refreshable braille displays.
Breadcrumb
A navigational aid that shows the page’s position in the hierarchy. Mark up with nav and aria-label="breadcrumb".
Button Role
ARIA role for clickable elements that trigger actions. Prefer native <button> elements when possible.
Bypass Blocks
Mechanisms such as skip links and landmarks that let users jump past repeated content directly to main sections.
C
Caption
Timed text for videos that transcribes speech and relevant sounds for people who are deaf or hard of hearing. Distinct from subtitles.
Carousel
A rotating banner of content. Often problematic for accessibility: ensure keyboard control, visible focus, pause/stop, and proper semantics.
Cerebral Palsy
Motor disability affecting movement and posture. Benefits from generous target sizes and alternative input methods.
Character Key Shortcuts
Single‑letter keyboard shortcuts that must be remappable, turned off, or only active on focus to prevent accidental activation.
Checkbox Role
ARIA role for dual-state controls. Support keyboard activation and clear checked/unchecked indication.
Closed Captions
Captions that can be toggled on/off by the user, containing dialogue and meaningful sounds synchronized with the video.
Cognitive Accessibility
Practices that improve comprehension and task completion for users with cognitive and learning disabilities, including plain language and consistency.
Cognitive Load
The mental effort required to process information or complete a task. Interfaces should minimize unnecessary complexity.
Color Contrast
The contrast ratio between foreground and background colors. WCAG requires 4.5:1 for body text and 3:1 for large text, icons, and UI.
Color Vision Deficiency (Color Blindness)
A range of conditions where certain colors are harder to distinguish. Designs must not rely on color alone to convey information.
Combobox
Input widget combining text field with popup list. Requires complex ARIA states and keyboard navigation patterns.
Complementary Role
ARIA landmark role for supporting content like sidebars, often containing related links or secondary information.
Content Reflow
Ability of content to adapt without loss of information or functionality when zoomed up to 400% or on small screens.
Contentinfo Role
ARIA landmark role for page footer content containing metadata, copyright, or secondary navigation.
Contrast Ratio
Numeric ratio expressing luminance difference between two colors. Common thresholds: 4.5:1 for normal text, 3:1 for large text or UI.
CVAA (21st Century Communications and Video Accessibility Act)
U.S. law requiring accessibility for advanced communications and video programming, including mobile apps and video players.
D
Deaf Culture
Community and identity of deaf individuals with shared language (sign language), values, and communication preferences.
Deafblind
Combined hearing and vision loss requiring tactile communication methods and specialized assistive technologies.
Device Independence
A property of interfaces that can be used with a variety of inputs (keyboard, touch, voice, switch), not requiring a specific device.
Dialog (Modal)
An overlay that requires user interaction before returning to the main UI. Must trap focus, label the dialog, and provide accessible dismissal.
Disclosure
A pattern to show or hide additional content, typically via a button that toggles aria-expanded and controls a region.
Dragon NaturallySpeaking
Voice recognition software enabling hands-free computer control and dictation for users with motor disabilities.
Dyslexia
A learning difference affecting reading and spelling. Designs benefit from clear typography, spacing, and predictable layouts.
E
EN 301 549
European standard defining accessibility requirements for ICT products and services, closely aligned with WCAG.
Error Identification
WCAG requirement to clearly identify and describe input errors to users in text form.
Error Prevention
Design patterns that reduce mistakes (confirmation, reversible actions, previews) required for important transactions by WCAG.
Error Recovery
Clear, actionable guidance to fix mistakes, including inline error messages associated with inputs via aria-describedby.
European Accessibility Act (EAA)
EU legislation requiring accessibility for key products and services. Complements EN 301 549 requirements.
Extended Description
Detailed alternative content for complex images, charts, or diagrams, often provided via adjacent text or modal.
F
Focus Indicator (Focus Visible)
A visible outline or style that shows which element has keyboard focus. WCAG requires adequate contrast and size.
Focus Management
Strategies to set and maintain focus order during dynamic changes such as modals, route transitions, and component mounts.
Focus Order
Sequential navigation order when using Tab key. Should be logical and match visual reading flow.
Form Label
Text associated with an input that communicates its purpose. Implement with <label for> or ARIA labelling.
Form Role
ARIA landmark role for form regions. Use when form lacks a native form element or needs additional identification.
G
Gestures (Pointer Gestures)
Actions like pinch, swipe, or drag. WCAG requires a single-pointer alternative that does not depend on complex gestures.
Grid Role
ARIA role for interactive tabular data where cells are focusable and may be editable, requiring 2D navigation.
Gridcell Role
ARIA role for individual cells within a grid, supporting focus and potentially editing capabilities.
Guideline
In WCAG, a guideline groups related success criteria under the POUR principles and provides intent and techniques.
H
Hard of Hearing
Partial hearing loss. May benefit from captions, visual alerts, and audio enhancement features.
Heading Role
ARIA role with aria-level attribute for custom headings when semantic HTML headings are insufficient.
Headings and Hierarchy
Semantic structure using h1–h6 to convey document outline. Avoid skipping levels and use headings to label sections.
High Contrast Mode
Operating system display mode that increases contrast. Respect system preferences and ensure custom styles remain legible.
Hover Content
Transient content that appears on hover or focus, which must be dismissible, hoverable, and persistent while being hovered.
I
Image Description (Long Description)
Extended text that conveys complex visual content such as charts or infographics, linked from the image or adjacent text.
Image of Text
Text presented within an image instead of actual characters. Generally discouraged; use real text where possible.
Input Assistance
Form helpers like labels, instructions, formatting hints, and auto-complete that help users enter information accurately.
Input Modality
Method of interaction (keyboard, mouse, touch, voice). Interfaces should support multiple modalities.
Intellectual Disability
Condition affecting intellectual functioning and adaptive behavior. Benefits from simplified language and clear navigation.
J
K
Keyboard Accessibility
Ensuring all interactive functionality is available through keyboard interface alone, without requiring mouse or touch.
Keyboard Navigation
The ability to operate all functionality using a keyboard alone. Requires logical tab order, focus styles, and skip links.
Keyboard Trap
A defect where focus cannot be moved away using the keyboard. Users must be able to navigate away with standard keys.
L
Landmark Regions
Page sections identified by semantic elements or ARIA roles (main, navigation, complementary, banner, contentinfo) for quick navigation.
Learning Disability
Conditions affecting information processing. Designs benefit from multiple presentation modes and clear structure.
Lighthouse Accessibility Audit
Built-in Chrome DevTools accessibility testing powered by axe-core, providing automated accessibility scoring.
Link Purpose
The destination or action of a link must be clear from its text or accessible name and its context.
Link Role
ARIA role for navigation elements. Prefer native <a> elements with proper href attributes.
List Role
ARIA role for grouping related items, used with listitem role elements.
Listitem Role
ARIA role for individual items within a list container.
Live Region
Dynamic content area that announces updates to assistive technologies without moving focus.
Logical Reading Order
The sequence in which content is read by assistive tech and reached by focus should match the visual and semantic order.
Low Vision
Significant visual impairment not correctable by glasses. Benefits from magnification, high contrast, and large text.
M
Magnification (Zoom)
Browser and OS zoom that enlarges content. Interfaces must remain usable and not block zoom.
Main Role
ARIA landmark role for primary content area. Should be unique per page and contain the main topic.
Meaningful Sequence
Content order that preserves meaning and operability when styles change or linearized for assistive technologies.
Menu Role
ARIA role for application menus with specific keyboard navigation patterns (arrow keys, escape).
Menubar Role
ARIA role for horizontal menu container, typically containing menu items or submenus.
Menuitem Role
ARIA role for individual options within a menu widget.
Motion Sensitivity (Photosensitivity)
Sensitivity to motion or flashing content. Respect prefers-reduced-motion and avoid seizure-triggering flashes.
Motor Disability
Physical impairment affecting movement, dexterity, or stamina. Benefits from keyboard access and generous target sizes.
N
Name, Role, Value
Information that assistive technologies must be able to determine for interactive components to ensure operability.
Navigation Role
ARIA landmark role for groups of navigation links to other pages or parts within the page.
Neurodiversity
Recognition that neurological differences like ADHD, autism, and dyslexia are natural variations requiring inclusive design.
NVDA
NonVisual Desktop Access: a free Windows screen reader with broad usage among blind and low-vision users.
O
Openness of Controls
Controls should not require precise pointer targeting; provide generous hit areas and visible affordances.
Option Role
ARIA role for selectable items within listbox, combobox, or similar selection widgets.
Orientation
Content and functionality should not be restricted to one display orientation unless essential.
P
Pa11y
Command-line accessibility testing tool that can be integrated into development workflows and CI/CD pipelines.
Perceivable
One of the four WCAG POUR principles: information and UI components must be presented in ways users can perceive.
Playwright Accessibility Testing
Automated accessibility testing within Playwright browser automation, often using axe-playwright integration.
Pointer Cancellation
Design that allows users to cancel or undo pointer actions to prevent accidental activation.
Presentation Role
ARIA role that removes semantic meaning from elements, making them invisible to assistive technologies.
Programmatic Label
Form label associated to inputs via label for/id, aria-label, or aria-labelledby so assistive technologies announce purpose.
Progressbar Role
ARIA role for progress indicators, requiring aria-valuenow and optionally aria-valuemin/aria-valuemax.
Progressive Enhancement
Build for the simplest, most robust experience first, then layer advanced features so the core remains accessible.
Q
Quality Alternative Text
Alt text that is accurate, concise, and task-focused, describing purpose rather than appearance.
Quality Assurance (QA) Accessibility
Testing processes to verify accessibility requirements are met throughout the development lifecycle.
Quick Navigation Keys
Screen reader feature to move by headings, landmarks, lists, and other structures using single-letter keys.
R
Radio Role
ARIA role for single-selectable options within a group. Use with radiogroup role container.
Radiogroup Role
ARIA role for grouping related radio button options where only one can be selected.
Readable Content
Plain language, short sentences, and clear structure that improves comprehension for everyone, especially cognitive disabilities.
Reduced Motion Preference
A user preference indicating they prefer limited motion. Use CSS media query prefers-reduced-motion to respect it.
Reflow
Requirement that content supports 320 CSS px viewport width without loss of information or functionality and without horizontal scroll.
Region Role
ARIA landmark role for significant page sections that users might want to navigate to. Requires accessible name.
Robust
Fourth WCAG POUR principle: content must work with various assistive technologies and remain functional as technologies advance.
Role
ARIA attribute that defines an element’s type to assistive tech. Prefer native HTML roles before adding ARIA roles.
S
Screen Magnifier
Assistive technology that enlarges content on screen, often with enhanced tracking and contrast features.
Screen Reader
Assistive technology that converts on-screen text and semantics to speech or braille output.
Search Role
ARIA landmark role for search functionality regions within a page.
Section 508
U.S. federal law requiring accessibility for government ICT, updated in 2018 to incorporate WCAG 2.0 Level AA.
Semantic HTML
Using HTML elements for their intended purpose to convey meaning and relationships, forming the foundation of accessibility.
Sensor Inputs
Inputs from motion, orientation, or location sensors. Provide alternatives that do not require device motion.
Skip Link
An in-page link placed early in the DOM that jumps directly to the main content, aiding keyboard and screen reader users.
Slider Role
ARIA role for range input controls, requiring aria-valuenow and keyboard increment/decrement support.
Spinbutton Role
ARIA role for numeric input with increment/decrement buttons or keyboard arrow support.
Status Message
Non-interruptive updates, like success alerts, announced to assistive tech using aria-live or role="status".
Subtitle
Timed text for videos that translates speech into another language and usually omits non-speech audio cues.
Sufficient Techniques
Documented methods from W3C that reliably meet a WCAG success criterion when properly implemented.
Switch Role
ARIA role for on/off toggle controls, similar to checkbox but representing state rather than selection.
T
Tab Order
The sequence focus follows when users press Tab. It should match the visual reading order and never be manipulated with positive tabindex.
Tab Role
ARIA role for tab navigation elements, used with tablist and tabpanel roles.
Tabindex
HTML attribute controlling focus order and focusability. Use -1 for programmatic focus, avoid positive values.
Tablist Role
ARIA role for container of tab elements, requiring arrow key navigation between tabs.
Tabpanel Role
ARIA role for content area associated with a tab, revealed when the tab is selected.
Tabs Pattern
UI pattern using tablist, tab, and tabpanel roles with arrow key navigation and automatic tab activation.
Target Size
Minimum recommended dimensions for interactive controls to ensure comfortable touch and pointer operation.
TENS (Transcutaneous Electrical Nerve Stimulation)
Pain management device that may affect sensitivity to touch interfaces and vibration feedback.
Text Alternatives
Equivalent text for non-text content such as images, icons, and media, enabling access by assistive technologies.
Textbox Role
ARIA role for text input elements, supporting both single-line and multiline configurations.
Timeouts
Session time limits must warn users, allow extension, or be essential. Provide clear timers and recovery paths.
Toast Notification
Temporary message overlay. Must be announced to screen readers via live regions and be dismissible.
Toolbar Role
ARIA role for grouping interactive controls, typically with arrow key navigation.
Tooltip
Contextual popup triggered by hover or focus. Must be keyboard accessible and dismissible.
Tree Role
ARIA role for hierarchical list structures with expandable/collapsible nodes.
Treeitem Role
ARIA role for individual nodes within a tree widget, supporting selection and expansion states.
U
Understandable
A WCAG POUR principle: interfaces must be clear and interactions predictable to minimize confusion or errors.
Universal Design
Designing products for the broadest range of users without adaptation, benefitting people with and without disabilities.
Usability Testing
Testing method involving real users to evaluate effectiveness, efficiency, and satisfaction of interfaces.
User Testing (Accessibility)
Evaluations that involve people with disabilities to validate real-world usability beyond automated and expert reviews.
V
Valid HTML
Standards-compliant markup that avoids errors. Validity improves parsing by assistive technologies and user agents.
Visual Presentation
Control of foreground/background color, line spacing, and text size to support readability and preference customization.
Voice Control
Input method that allows users to operate interfaces via speech. Controls need clear labels and visible text for command recognition.
VoiceOver
Built-in screen reader for macOS and iOS devices, providing speech and braille output.
VPAT (Voluntary Product Accessibility Template)
Document format for reporting product accessibility conformance against standards like WCAG, Section 508, or EN 301 549.
W
WAI-ARIA Authoring Practices (APG)
W3C guidance on building accessible widgets and patterns using ARIA in conjunction with semantic HTML.
WAVE (Web Accessibility Evaluation Tool)
Browser extension and online tool by WebAIM for visual accessibility evaluation and error identification.
WCAG (Web Content Accessibility Guidelines)
International standard defining success criteria for accessible web content, currently at version 2.x with levels A, AA, AAA.
WCAG Conformance Level
Levels A, AA, AAA indicate increasing strictness of success criteria met by content; most policies require at least AA.
Web Accessibility Initiative (WAI)
W3C initiative developing accessibility guidelines, techniques, and resources including WCAG and ARIA.
Web Vitals and Accessibility
Performance metrics (LCP, CLS, INP) intersect with accessibility by ensuring fast, stable, and responsive experiences.
WebAIM Contrast Checker
A common tool to verify color contrast ratios meet WCAG requirements for text and UI components.
Windows Narrator
Built-in Windows screen reader providing basic accessibility features for system navigation and web browsing.