Accessibility Glossary

154+ terms covering WCAG, ARIA, assistive technology, legal standards, and web accessibility best practices. Click a letter to jump to that section.

A

Accessibility Audit: A systematic evaluation of a digital product against accessibility standards such as WCAG 2.1 or Section 508. Audits typically combine automated scanning with manual testing by assistive technology users to identify barriers and produce a remediation report.See also: WCAG (Web Content Accessibility Guidelines), Section 508, Remediation
Accessibility Conformance Report (ACR): A document that formally declares how a product or service conforms to accessibility standards. ACRs are typically based on the VPAT template and submitted by vendors to government agencies and enterprise buyers evaluating accessible technology procurement.See also: VPAT (Voluntary Product Accessibility Template), WCAG (Web Content Accessibility Guidelines), Section 508
Accessible Authentication: WCAG 3.3.8 (Level AA) and 3.3.9 (Level AAA, added in WCAG 2.2): authentication processes must not rely solely on cognitive function tests (such as transcribing text, solving puzzles, or memorizing a sequence) unless an alternative is provided, a mechanism is available to assist, or the test is used to identify objects.See also: Cognitive Disability, Understandable, WCAG 2.2
Accessible Document: A file (PDF, Word, Excel, etc.) structured so that assistive technologies can read and navigate its content. Key requirements include document titles, heading structure, alt text for images, reading order, and tagged PDF format for PDF files.See also: Tagged PDF, PDF Accessibility, Alt Text
Accessible Name: The human-readable label associated with a user interface element, computed by the browser from visible text, aria-label, aria-labelledby, or the HTML for attribute. Screen readers announce the accessible name when a user focuses the element.See also: aria-label, aria-labelledby, Screen Reader
ACR: Short for Accessibility Conformance Report. A structured declaration of a product's conformance to accessibility standards, typically based on the VPAT template. Federal agencies and large enterprises often require ACRs during technology procurement.See also: Accessibility Conformance Report (ACR), VPAT (Voluntary Product Accessibility Template)
ADA (Americans with Disabilities Act): A US civil rights law enacted in 1990 prohibiting discrimination against people with disabilities in all areas of public life. Title III covers businesses open to the public, and courts and the DOJ have interpreted it to apply to websites and mobile apps.See also: ADA Title II, Section 508, Reasonable Accommodation
ADA Title II: The section of the Americans with Disabilities Act that applies to state and local government entities. In 2024, the DOJ issued final rules requiring state/local governments to meet WCAG 2.1 AA for their websites and mobile apps, with deadlines from 2026 to 2027.See also: ADA (Americans with Disabilities Act), WCAG (Web Content Accessibility Guidelines), Section 508
Advisory Techniques: Suggested WCAG implementation methods that go beyond minimum requirements and are not required for conformance. Following advisory techniques improves the user experience for people with disabilities beyond what WCAG mandates.See also: Sufficient Techniques, WCAG (Web Content Accessibility Guidelines), Success Criterion
Alt Text: Short for alternative text, the text equivalent of an image conveyed through the HTML alt attribute. Screen readers announce alt text to blind users. Decorative images should use an empty alt attribute (alt="") so screen readers skip them.See also: Screen Reader, Perceivable, WCAG (Web Content Accessibility Guidelines)
AODA (Accessibility for Ontarians with Disabilities Act): Ontario, Canada's accessibility law requiring organizations with 50 or more employees to meet WCAG 2.0 Level AA for websites and web content. The deadline for compliance has passed (January 2021 for large organizations), making it an active enforcement area.See also: WCAG (Web Content Accessibility Guidelines), EN 301 549
ARIA (Accessible Rich Internet Applications): A W3C technical specification that defines attributes (roles, states, and properties) for enhancing the accessibility of HTML elements. ARIA supplements native HTML semantics but cannot replace them — it is most valuable for dynamic widgets where native HTML lacks sufficient semantics.See also: aria-label, aria-live, Landmark Roles, Widget Roles
aria-describedby: An ARIA attribute that associates an element with one or more elements providing additional descriptive information. Screen readers typically announce the referenced description after the element's accessible name, giving users context beyond the label.See also: aria-labelledby, aria-label, Accessible Name
aria-expanded: An ARIA state attribute indicating whether an expandable element (such as a disclosure widget, accordion, or tree node) is currently expanded or collapsed. Screen readers announce the expanded/collapsed state when users interact with accordions, dropdown menus, and navigation trees.See also: ARIA (Accessible Rich Internet Applications), aria-hidden, Widget Roles
aria-hidden: An ARIA attribute that removes an element and its children from the accessibility tree, hiding them from assistive technologies. Used for decorative icons, repeated content, or elements that convey meaning through visual context alone.See also: ARIA (Accessible Rich Internet Applications), Accessible Name, Screen Reader
aria-label: An ARIA attribute that provides a text label for an element when a visible label is not present or is insufficient. It overrides the element's computed accessible name with the value provided. Commonly used on icon buttons and landmark regions.See also: aria-labelledby, Accessible Name, ARIA (Accessible Rich Internet Applications)
aria-labelledby: An ARIA attribute that associates an element's accessible name with one or more existing visible elements on the page. It references element IDs and takes precedence over aria-label and native labeling methods in the accessibility name computation.See also: aria-label, aria-describedby, Accessible Name
aria-live: An ARIA attribute that marks a region of the page that will receive dynamic content updates. Screen readers monitor live regions and announce changes automatically. Values include "polite" (announces after user finishes current task) and "assertive" (interrupts immediately).See also: ARIA (Accessible Rich Internet Applications), Screen Reader, Operable
aria-required: An ARIA property indicating that user input is required before a form may be submitted. The HTML required attribute is preferred when available; aria-required is used for custom form controls that do not map to native HTML form elements.See also: ARIA (Accessible Rich Internet Applications), Form Labels, Error Identification
aria-selected: An ARIA state attribute indicating that a selectable element (such as a tab, option, or tree item) is currently selected. Used in conjunction with widget roles like tab, option, and treeitem to communicate selection state to assistive technologies.See also: ARIA (Accessible Rich Internet Applications), Widget Roles, Accessible Name
Assistive Technology: Hardware or software that helps people with disabilities use computers and digital content. Examples include screen readers (JAWS, NVDA, VoiceOver), magnification software, switch access devices, refreshable braille displays, and alternative keyboards.See also: Screen Reader, JAWS (Job Access With Speech), NVDA (NonVisual Desktop Access), VoiceOver, Braille Display
Audio Description: A narration track added to video content that describes important visual information for users who are blind or have low vision. Describes actions, characters, scene changes, and on-screen text that are not conveyed through the dialogue or soundtrack.See also: Captions, Perceivable, WCAG (Web Content Accessibility Guidelines)
Automated Testing: Using software tools to automatically scan web pages and identify accessibility issues. Automated tools can catch approximately 30–40% of WCAG failures. The remaining issues require manual testing, assistive technology testing, and user testing with people who have disabilities.See also: axe-core, Lighthouse, WAVE (Web Accessibility Evaluation Tool), Accessibility Audit
axe-core: An open-source accessibility testing library created by Deque Systems. It powers many accessibility testing tools including the axe DevTools browser extension, pa11y, and Lighthouse. It tests web pages against WCAG criteria and generates structured violation reports.See also: Lighthouse, WAVE (Web Accessibility Evaluation Tool), pa11y, Accessibility Audit

B

Braille Display: An electro-mechanical output device that renders text and some graphics as refreshable braille cells, allowing users who are blind or deafblind to read digital content tactilely. Braille displays connect to computers and mobile devices and work in tandem with screen readers.See also: Screen Reader, Assistive Technology
Button vs. Link: A fundamental accessibility distinction: links (<a>) navigate to a new location or resource; buttons (<button>) trigger an action on the current page. Using the wrong element breaks screen reader user expectations and can impair keyboard operability. Use CSS to style them differently, not to repurpose their semantics.See also: Semantic HTML, Keyboard Navigation, Operable
Bypass Blocks: WCAG 2.4.1 (Level A): a mechanism must be available to bypass blocks of content that are repeated on multiple pages. Typically implemented as a skip navigation link at the top of the page, allowing keyboard users to jump directly to the main content.See also: Skip Navigation, Keyboard Navigation, Operable

C

Captions: Text alternatives for audio content in video, including spoken dialogue, speaker identification, and important non-speech sounds. Closed captions can be turned on or off by the user; open captions are permanently embedded in the video.See also: Audio Description, Perceivable, WCAG (Web Content Accessibility Guidelines)
Cognitive Disability: A broad category of conditions that affect learning, memory, attention, problem-solving, or communication. In web accessibility, design considerations include plain language, consistent navigation, predictable behavior, error prevention and recovery, and avoiding unnecessary complexity.See also: Understandable, WCAG (Web Content Accessibility Guidelines), Plain Language
Color Blindness: A visual condition affecting the ability to distinguish certain color combinations, most commonly red-green. Affects approximately 8% of males and 0.5% of females. Accessible design never conveys information through color alone — it must also use text, patterns, or symbols.See also: Color Contrast, Perceivable, Visual Impairment
Color Contrast: The difference in luminance between text (or UI component) and its background, measured as a ratio. WCAG 2.1 AA requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text (18pt or 14pt bold). The enhanced AAA level requires 7:1 for normal text.See also: Color Blindness, Perceivable, WCAG (Web Content Accessibility Guidelines)
Color Contrast Analyzer: A tool that measures the luminance contrast ratio between two colors to verify compliance with WCAG color contrast requirements. Popular tools include the TPGi Color Contrast Analyser (desktop app), WebAIM Contrast Checker (web tool), and browser DevTools accessibility panels.See also: Color Contrast, Perceivable, WAVE (Web Accessibility Evaluation Tool)
Color Independence: The principle that information must never be conveyed by color alone. WCAG 1.4.1 requires that color is not the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. Always add text, patterns, icons, or shapes as secondary indicators.See also: Color Blindness, Perceivable, WCAG (Web Content Accessibility Guidelines)
Compliance Report: A formal document summarizing an organization's adherence to accessibility standards and regulations. Compliance reports may include scan results, manual testing findings, remediation timelines, and attestations of conformance for regulatory or procurement purposes.See also: Accessibility Conformance Report (ACR), VPAT (Voluntary Product Accessibility Template), Accessibility Audit
Conformance Level: The level of WCAG compliance a website achieves: Level A (minimum, 30 success criteria), Level AA (standard, adds 20 criteria), or Level AAA (enhanced, adds 28 criteria). Most legal standards and procurement requirements mandate WCAG 2.1 AA conformance.See also: WCAG (Web Content Accessibility Guidelines), Success Criterion, VPAT (Voluntary Product Accessibility Template)
Consistent Navigation: WCAG 3.2.3 (Level AA): navigational mechanisms that appear on multiple pages in a set of web pages must occur in the same relative order each time they are repeated, unless the user initiates a change. Consistent navigation reduces cognitive load for users with cognitive disabilities.See also: Understandable, WCAG (Web Content Accessibility Guidelines), Cognitive Disability
Content on Hover or Focus: WCAG 1.4.13 (Level AA, added in 2.1): additional content that appears on hover or focus (like tooltips) must be dismissible, hoverable, and persistent. Users must be able to dismiss the new content without moving focus, move the pointer over it, and rely on it remaining visible as long as they need.See also: Perceivable, WCAG 2.1, Keyboard Navigation
Contrast Checker: A tool that calculates the luminance contrast ratio between two colors and indicates whether the combination passes WCAG AA (4.5:1 text, 3:1 large text) or AAA (7:1 text) thresholds. Most are free web tools or browser extensions.See also: Color Contrast Analyzer, Color Contrast, Accessibility Audit
Contrast Ratio: A mathematical expression of the difference in perceived luminance between two colors, expressed as a ratio (e.g., 4.5:1). Calculated using the WCAG relative luminance formula. A ratio of 1:1 means no contrast (same color); 21:1 is maximum contrast (black on white).See also: Color Contrast, Perceivable, Non-text Contrast
CSS Accessibility: CSS (Cascading Style Sheets) accessibility refers to styling practices that support accessible interfaces. This includes not relying on CSS alone to convey information, ensuring focus indicators are visible, supporting high-contrast mode, and avoiding styles that remove inherent browser focus styling.See also: Focus Indicator, Reflow, Operable

D

Descriptive Headings: WCAG 2.4.6 (Level AA): headings must describe the topic or purpose of the section they introduce. Descriptive headings help users with screen readers navigate a document and understand its structure before reading the full content of each section.See also: Heading Hierarchy, Operable, WCAG (Web Content Accessibility Guidelines)
Descriptive Link Text: Link text that describes the destination or purpose of the link out of context. WCAG 2.4.4 requires links to have a purpose that can be determined from the link text alone or from the link's context. Avoid generic phrases like "click here" or "read more" that are meaningless when read in isolation.See also: Screen Reader, Operable, WCAG (Web Content Accessibility Guidelines)
Dialog (Modal): A pop-up window that requires user interaction before continuing. Accessible modals must move keyboard focus into the dialog on open, trap focus within the dialog while open, and return focus to the trigger element on close. The ARIA dialog role is required for custom implementations.See also: Focus Management, ARIA (Accessible Rich Internet Applications), Keyboard Trap
Document Language: WCAG 3.1.1 (Level A): the default human language of each web page must be programmatically determined. The lang attribute on the <html> element allows screen readers to switch pronunciation engines correctly. WCAG 3.1.2 requires the language to be identified for content passages in different languages.See also: Understandable, Screen Reader, WCAG (Web Content Accessibility Guidelines)
DOM (Document Object Model): A programming interface that represents an HTML or XML document as a tree structure. Accessibility is determined by the DOM tree — the order elements appear in the DOM controls reading order for screen readers, independent of visual CSS layout.See also: Screen Reader, Semantic HTML, tabindex

E

EAA (European Accessibility Act): EU Directive 2019/882 requiring products and services sold in EU member states to be accessible. It covers digital products including websites, mobile apps, e-commerce, banking, e-books, and electronic communications. The compliance deadline for businesses is June 28, 2025.See also: EN 301 549, WCAG (Web Content Accessibility Guidelines), AODA (Accessibility for Ontarians with Disabilities Act)
Empty Alt Attribute: An alt attribute with an empty string value (alt="") that tells assistive technologies to ignore an image. Used for decorative images, icons used alongside visible text labels, or images that convey no additional information. An img element without any alt attribute is an accessibility error.See also: Alt Text, aria-hidden, Perceivable
EN 301 549: The European standard for accessibility requirements for ICT products and services, published by ETSI. It references WCAG 2.1 AA for web content and adds requirements for hardware, software, and documentation. EN 301 549 is the technical standard that underpins the European Accessibility Act.See also: EAA (European Accessibility Act), WCAG (Web Content Accessibility Guidelines), Section 508
Enhanced Color Contrast (AAA): WCAG 1.4.6 (Level AAA): the visual presentation of text requires a contrast ratio of at least 7:1 for normal text and 4.5:1 for large text. The enhanced level (AAA) goes beyond the AA requirement of 4.5:1 and is recommended for public-facing content serving users with severe low vision.See also: Color Contrast, Visual Impairment, WCAG (Web Content Accessibility Guidelines)
Error Identification: WCAG Success Criterion 3.3.1: when an input error is automatically detected, the item that is in error is identified and the error is described to the user in text. This ensures users with screen readers receive specific, actionable feedback rather than generic error messages.See also: Form Labels, Understandable, WCAG (Web Content Accessibility Guidelines)
Error Prevention: WCAG 3.3.4 (Level AA): for web pages that cause legal commitments, financial transactions, or modifications of user data, submissions must be reversible, checked for errors, or confirmed by the user. Reduces harm from accidental submissions by users with cognitive or motor disabilities.See also: Error Identification, Understandable, WCAG (Web Content Accessibility Guidelines)

F

Fieldset and Legend: HTML elements used to group related form controls. The <fieldset> element groups the controls, and the <legend> element provides a visible and programmatically associated label for the group. Required for radio button groups and checkboxes that share a common question.See also: Form Labels, Semantic HTML, WCAG (Web Content Accessibility Guidelines)
Flashing Content (Seizure Risk): WCAG 2.3.1 requires web pages to contain no content that flashes more than three times per second, as such content can trigger photosensitive seizures. Flashing content is one of the most severe accessibility barriers and can cause physical harm.See also: Perceivable, Operable, WCAG (Web Content Accessibility Guidelines)
Focus Appearance: WCAG 2.4.13 (Level AAA, added in WCAG 2.2): the focus indicator must meet minimum area and contrast requirements. Specifically, the focus indicator must have an area at least as large as a 2px perimeter around the focused component and a contrast ratio of at least 3:1 between the focused and unfocused states.See also: Focus Indicator, WCAG 2.2, Operable
Focus Indicator: The visible cue — typically a border, outline, or highlight — that shows which interactive element has keyboard focus. WCAG 2.1 AA requires focus to be visible (SC 2.4.7). WCAG 2.2 adds Focus Not Obscured (2.4.11) requiring the focused component to not be entirely hidden.See also: Keyboard Navigation, Operable, Tab Order
Focus Management: The practice of programmatically controlling where keyboard focus moves in response to user actions. Essential for single-page applications, modals, and dynamic content — when a modal opens, focus should move into it; when it closes, focus should return to the trigger element.See also: Focus Indicator, Keyboard Trap, aria-live
Focus Order: WCAG 2.4.3 (Level A): if a web page can be navigated sequentially and the navigation sequences affect meaning or operation, focusable components must receive focus in an order that preserves meaning and operability. The focus order should match the visual reading order.See also: Tab Order, Keyboard Navigation, Focus Indicator
Focus Visible (Resting State): WCAG 2.4.11 (WCAG 2.2, AA): the component that receives keyboard focus is not entirely hidden by author-created content. The focused item must be at least partially visible in the viewport, ensuring users can see where focus is when navigating by keyboard.See also: Focus Indicator, Operable, WCAG (Web Content Accessibility Guidelines)
Form Labels: Visible text that identifies each form control (input, select, textarea) and is programmatically associated with it using the HTML for attribute or by wrapping the control. Properly labeled controls are announced by screen readers and help all users understand what information to provide.See also: Fieldset and Legend, Accessible Name, Error Identification

G

Graceful Degradation: A design philosophy where a system continues to operate at a reduced level of functionality when part of it fails. In accessibility, graceful degradation means a page remains usable when JavaScript fails, CSS does not load, or an assistive technology has limited support for a feature.See also: Robust, WCAG (Web Content Accessibility Guidelines), Semantic HTML

H

Heading Hierarchy: The logical ordering of heading elements (h1 through h6) in an HTML document. A proper hierarchy starts with a single h1, then uses h2 for major sections, h3 for subsections, and so on without skipping levels. Screen reader users navigate by headings to understand structure and jump to content.See also: Semantic HTML, Screen Reader, Perceivable
Heading Navigation: A technique used by screen reader users to navigate a page by jumping between heading elements using keyboard shortcuts. Screen readers allow users to list all headings or jump to the next heading of any level. Proper heading hierarchy is essential for this navigation technique to be useful.See also: Heading Hierarchy, Screen Reader, Landmark Roles
Hearing Impairment: A broad term covering partial or total loss of hearing. Web accessibility accommodations include captions for video, transcripts for audio-only content, and visual alternatives to audio alerts. Sign language interpretation is an AAA-level WCAG provision.See also: Captions, Audio Description, Perceivable
High Contrast Mode: An operating system or browser setting that overrides color schemes to use high-contrast colors for better visibility. Windows high contrast mode replaces CSS colors with system colors. Accessible sites support this by not hiding focus indicators and not relying solely on background images for content.See also: Color Contrast, Visual Impairment, CSS Accessibility
HTML Validation: The process of checking HTML markup against the W3C specification to identify syntax errors. While WCAG 4.1.1 (Parsing) was deprecated in WCAG 2.2, valid HTML remains important for consistent browser rendering and assistive technology support.See also: Robust, Semantic HTML, WCAG 2.2

I

ICT (Information and Communications Technology): Technology used to handle information, including computers, software, mobile devices, telecommunications, and the internet. Section 508 mandates that federal agencies make ICT accessible. The term ICT is used in both Section 508 and EN 301 549 to describe the scope of accessibility requirements.See also: Section 508, EN 301 549, Accessibility Audit
Identify Input Purpose: WCAG 1.3.5 (Level AA, added in 2.1): the purpose of form inputs collecting information about the user (name, address, email, etc.) must be programmatically determinable using the HTML autocomplete attribute. Enables browsers and assistive technologies to autofill inputs and present appropriate icons.See also: Form Labels, Perceivable, WCAG 2.1
Images of Text: WCAG 1.4.5 (Level AA): images that contain text should be avoided unless the visual presentation is essential (such as logos) or the image can be customized. Images of text cannot be resized without pixelation and do not honor user text style preferences.See also: Perceivable, Alt Text, Low Vision
Inaccessible CAPTCHA: Traditional visual CAPTCHAs that require users to identify distorted text or images create barriers for users who are blind, have low vision, or cognitive disabilities. Accessible alternatives include audio CAPTCHAs, logical questions, honeypot fields, or time-based analysis.See also: Cognitive Disability, Visual Impairment, WCAG (Web Content Accessibility Guidelines)
Inclusive Design: A design methodology that creates products usable by the widest range of people without the need for adaptation or specialized design. It differs from accessibility (which focuses on specific disabilities) by considering all human diversity — ability, language, culture, age, and gender — from the start.See also: Universal Design, WCAG (Web Content Accessibility Guidelines), WCAG Principles (POUR)

J

JavaScript Accessibility: Practices for building accessible JavaScript-enhanced interfaces. Includes managing focus in dynamic content, using ARIA live regions for announcements, ensuring keyboard operability of custom widgets, and avoiding JavaScript techniques that break browser accessibility APIs.See also: aria-live, Focus Management, Operable
JAWS (Job Access With Speech): A Windows screen reader developed by Freedom Scientific, widely used in enterprise and government environments. JAWS is considered the most feature-rich Windows screen reader and is frequently used in formal accessibility testing because of its prevalence among professional screen reader users.See also: Screen Reader, NVDA (NonVisual Desktop Access), Assistive Technology
Justified Text and Hyphenation: Fully justified text creates uneven word spacing that reduces readability for users with dyslexia. WCAG does not explicitly ban justified text, but it recommends left-aligned text in understanding documents. CSS text-align: justify should be avoided on body text in accessible designs.See also: Cognitive Disability, Perceivable, Plain Language

K

Keyboard Navigation: The ability to interact with all parts of a website using only a keyboard, without a mouse or touch screen. WCAG Principle 2 (Operable) requires all functionality to be accessible via keyboard. Tab, Shift+Tab, Enter, Space, and arrow keys are the primary navigation mechanisms.See also: Focus Indicator, Tab Order, Keyboard Trap
Keyboard Shortcut: A key combination that triggers an action. WCAG 2.1.4 requires that single-character keyboard shortcuts can be turned off, remapped, or only activated when focus is on the component — preventing conflicts with screen reader and browser shortcuts.See also: Keyboard Navigation, Operable, WCAG (Web Content Accessibility Guidelines)
Keyboard Trap: A situation where keyboard focus becomes stuck inside a component and users cannot navigate away using standard keyboard commands. WCAG 2.1.2 prohibits keyboard traps — unless the trap is intentional (e.g., a modal dialog) and users are informed of alternative keyboard commands to escape.See also: Keyboard Navigation, Focus Management, Operable

L

Label in Name: WCAG 2.5.3 (Level A, added in WCAG 2.1): for UI components with a visible text label, the accessible name must contain the visible text. This prevents a situation where a button reads "Submit form" visually but its aria-label says "Next" — breaking voice control navigation.See also: Accessible Name, aria-label, WCAG 2.1
Label Placement: The visual position of form labels relative to their controls affects usability and accessibility. Best practice places labels above inputs (mobile-friendly) or to the left. Placeholder text is not a substitute for visible labels because it disappears when users start typing.See also: Form Labels, Accessible Name, Understandable
Landmark Roles: ARIA roles that identify the primary regions of a page, such as banner (header), navigation, main, complementary (aside), and contentinfo (footer). Screen reader users can jump directly between landmark regions using keyboard shortcuts, dramatically improving navigation efficiency.See also: ARIA (Accessible Rich Internet Applications), Screen Reader, Semantic HTML
Lighthouse: An open-source automated auditing tool developed by Google, available in Chrome DevTools and as a CLI. Its accessibility audits are powered by axe-core and cover a subset of WCAG criteria. Lighthouse generates a 0–100 accessibility score but cannot replace manual testing.See also: axe-core, WAVE (Web Accessibility Evaluation Tool), Accessibility Audit
List Semantics: Using HTML list elements (<ul>, <ol>, <li>, <dl>) for groups of related items. Screen readers announce the number of items in a list and allow navigation between items. Using div elements styled as lists removes this semantic information from the accessibility tree.See also: Semantic HTML, Screen Reader, Perceivable
Live Region: An ARIA pattern using aria-live or role="status" / role="alert" to announce dynamic content changes to screen reader users without requiring them to navigate to the updated content. Used for status messages, notifications, search results loading, and error summaries.See also: aria-live, Screen Reader, ARIA (Accessible Rich Internet Applications)
Low Vision: A visual impairment that cannot be fully corrected with glasses or contact lenses, causing reduced visual acuity or visual field. Users with low vision frequently use screen magnification, increased text size, and high contrast settings. Web accessibility accommodations include reflow support and text resizing.See also: Magnification, Visual Impairment, Reflow

M

Magnification: Software that enlarges all or part of the screen to make content visible for users with low vision. Common tools include ZoomText (Windows) and Zoom (macOS/iOS). WCAG requires that content can be resized up to 200% without loss of content or functionality (SC 1.4.4).See also: Low Vision, Reflow, Text Spacing
Mobile Accessibility: Accessibility practices specific to mobile devices and touchscreens, including sufficient touch target sizes (44x44px minimum), support for platform screen readers (VoiceOver, TalkBack), avoiding hover-only interactions, and supporting screen rotation. WCAG 2.1 added specific mobile success criteria.See also: Target Size (Minimum), VoiceOver, TalkBack
Motion and Animation: WCAG 2.3.3 (Level AAA): animation triggered by interaction can be disabled unless it is essential to functionality. CSS media query prefers-reduced-motion allows developers to honor user OS settings to reduce or eliminate animations, benefiting users with vestibular disorders and motion sensitivity.See also: Operable, Cognitive Disability, WCAG (Web Content Accessibility Guidelines)
Motor Disability: A condition affecting the ability to control physical movement. Motor disabilities can affect hand movement (limiting mouse use), speech production, or any combination of motor skills. Accessibility accommodations include full keyboard operability, adequate target sizes, and support for alternative input devices like switch access.See also: Switch Access, Keyboard Navigation, Operable

N

Name, Role, Value: WCAG 4.1.2 Success Criterion: all user interface components have a name and role that can be programmatically determined; states, properties, and values can be set by the user; and user agents including assistive technologies are notified of changes. This is the technical foundation of accessible custom widgets.See also: Accessible Name, ARIA (Accessible Rich Internet Applications), Robust
Navigation Landmarks: Specific HTML5 elements and ARIA landmark roles that divide a page into major regions: header, nav, main, aside, footer, search, form. Screen reader users can jump directly between landmarks using keyboard shortcuts, bypassing repetitive content efficiently.See also: Landmark Roles, Skip Navigation, Semantic HTML
Non-text Contrast: WCAG 1.4.11 (Level AA, added in 2.1): the visual presentation of UI components and graphical objects (like icons) must have a contrast ratio of at least 3:1 against adjacent colors. This extends contrast requirements beyond text to include form controls, focus indicators, and meaningful graphics.See also: Color Contrast, Perceivable, WCAG 2.1
NVDA (NonVisual Desktop Access): A free, open-source Windows screen reader developed by NV Access. NVDA is widely used among blind and visually impaired users and is a standard tool for accessibility testing. It supports web browsing, document reading, and application interaction.See also: Screen Reader, JAWS (Job Access With Speech), Assistive Technology

O

On Focus / On Input Behavior: WCAG 3.2.1 and 3.2.2: receiving focus or changing a form input must not cause unexpected context changes (like opening a new window or submitting a form). Unexpected behavior disorientsscreen reader users and keyboard users who may trigger focus or input unintentionally.See also: Understandable, Focus Indicator, Keyboard Navigation
Operable: The second WCAG principle: all UI components and navigation must be operable. This includes keyboard accessibility, sufficient time limits, avoidance of seizure-triggering content, and navigability. Operability ensures users can interact with all functionality regardless of their input method.See also: WCAG Principles (POUR), Keyboard Navigation, Perceivable
Orientation: WCAG 1.3.4 (Level AA, added in 2.1): content must not be restricted to a single display orientation (landscape or portrait) unless that orientation is essential. Some users mount tablets in fixed positions and cannot rotate their device; locking orientation to landscape or portrait creates a barrier.See also: Perceivable, WCAG 2.1, Motor Disability

P

pa11y: An open-source command-line accessibility testing tool that runs axe-core or HTML_CodeSniffer against URLs. Commonly used in CI/CD pipelines for automated regression testing. Supports custom standards, thresholds, and output formats.See also: axe-core, Lighthouse, Accessibility Audit
Page Title: The text in the HTML <title> element that appears in browser tabs and is announced by screen readers as the first piece of information on page load. WCAG 2.4.2 requires pages to have titles that describe their topic or purpose, helping users navigate between browser tabs and windows.See also: Semantic HTML, Perceivable, WCAG (Web Content Accessibility Guidelines)
PDF Accessibility: The practice of making PDF documents usable with screen readers and other assistive technologies. Key requirements include tagged PDF structure, reading order, alt text for images, document language, title metadata, and accessible forms.See also: Tagged PDF, Accessible Document, Screen Reader
Perceivable: The first WCAG principle: all information and UI components must be presentable to users in ways they can perceive. This covers text alternatives for non-text content, captions for multimedia, sufficient color contrast, and the ability to resize text without loss of functionality.See also: WCAG Principles (POUR), Alt Text, Color Contrast
Plain Language: Writing that is clear, concise, and easily understood by the target audience. For accessibility, plain language reduces cognitive load for users with cognitive disabilities, users whose native language differs from the content language, and users with lower literacy levels.See also: Cognitive Disability, Understandable, WCAG (Web Content Accessibility Guidelines)
Plain Text Alternative: A text representation of content that is presented in another format (such as a complex data table or infographic). WCAG 1.1.1 requires all non-text content to have a text alternative. For complex visuals, a short alt text plus a longer plain text alternative satisfies this requirement.See also: Alt Text, Perceivable, WCAG (Web Content Accessibility Guidelines)
Pointer Gestures: WCAG 2.5.1 (Level A, added in 2.1): all functionality using multipoint or path-based gestures (such as pinch-to-zoom or swipe) must also be operable with a single pointer without a path-based gesture. This supports users with motor disabilities who cannot perform complex gestures.See also: Operable, Motor Disability, WCAG 2.1
Programmatic Determination: The ability for user agents and assistive technologies to identify information from the source code (HTML, ARIA, etc.) — such as an element's role, state, name, or the language of the page. Programmatic determination is required for most accessibility implementations across all four WCAG principles.See also: Name, Role, Value, Semantic HTML, ARIA (Accessible Rich Internet Applications)

R

Reading Order: The sequence in which screen readers announce page content, determined by the order of elements in the DOM (not their visual position). Accessible pages ensure that DOM order matches the intended reading sequence so content is logical when linearized.See also: DOM (Document Object Model), Screen Reader, Semantic HTML
Reasonable Accommodation: A modification or adjustment to a job, work environment, or the way things are usually done that enables a qualified person with a disability to enjoy equal employment opportunities. In the context of digital accessibility, it refers to modifications that do not impose an undue burden on the organization.See also: Undue Burden, ADA (Americans with Disabilities Act), WCAG (Web Content Accessibility Guidelines)
Redundant Entry: WCAG 3.3.7 (Level A, added in WCAG 2.2): information previously entered by or provided to the user that is required again in the same process must be auto-populated or available for the user to select. This reduces cognitive load, especially for users with memory or attention difficulties.See also: Cognitive Disability, Understandable, WCAG 2.2
Reflow: WCAG 1.4.10: content must reflow into a single column when the viewport is 320px wide (equivalent to 400% zoom on a 1280px screen), without requiring horizontal scrolling to read a full line of text. Reflow support is essential for users who zoom their browsers to 400%.See also: Magnification, Low Vision, Perceivable
Remediation: The process of fixing accessibility barriers identified through an audit. Remediation may involve modifying HTML, adding ARIA attributes, updating CSS, rewriting content, or making structural changes. Effective remediation is typically tracked in a prioritized issues list with deadlines.See also: Accessibility Audit, WCAG (Web Content Accessibility Guidelines), Compliance Report
Robust: The fourth WCAG principle: content must be robust enough that it can be reliably interpreted by a wide variety of user agents, including current and future assistive technologies. This principle emphasizes valid HTML, parsing, and name/role/value for all user interface components.See also: WCAG Principles (POUR), Semantic HTML, ARIA (Accessible Rich Internet Applications)
role="presentation": An ARIA role that removes an element's implicit semantics from the accessibility tree while keeping the element and its children visible. Equivalent to role="none". Used to neutralize table layouts, decorative headings, or elements whose native role conflicts with their use in a pattern.See also: ARIA (Accessible Rich Internet Applications), aria-hidden, Semantic HTML
Roving tabindex: A keyboard navigation pattern for composite widgets (menus, toolbars, grids, trees) where only one item in the group is in the tab sequence at a time. Users move within the widget using arrow keys; Tab moves to the next widget outside the group. Prevents excessive Tab stops in complex UIs.See also: tabindex, Keyboard Navigation, Widget Roles

S

Screen Magnification Software: Software such as ZoomText (Windows) or Apple Zoom that enlarges the entire screen or a portion of it for users with low vision. Unlike browser zoom, magnification software works at the OS level across all applications. Accessible websites must reflow correctly at all zoom levels.See also: Magnification, Low Vision, Reflow
Screen Reader: Assistive technology software that converts text and other on-screen information into speech or braille output for users who are blind, have low vision, or have a reading disability. Popular screen readers include JAWS, NVDA, VoiceOver (Apple), and TalkBack (Android).See also: JAWS (Job Access With Speech), NVDA (NonVisual Desktop Access), VoiceOver, TalkBack, Assistive Technology
Section 508: A US federal law requiring that federal agencies make their electronic and information technology accessible to people with disabilities. Section 508 was significantly updated in 2018 (the "Refresh") to align with WCAG 2.0 Level AA. Federal contractors must also comply when their products are procured by agencies.See also: ADA (Americans with Disabilities Act), WCAG (Web Content Accessibility Guidelines), VPAT (Voluntary Product Accessibility Template)
Semantic HTML: The practice of using HTML elements according to their intended meaning — headings for structure, lists for collections, buttons for actions, links for navigation, and landmark elements for page regions. Semantic HTML provides built-in accessibility information to assistive technologies without requiring ARIA.See also: Heading Hierarchy, Landmark Roles, ARIA (Accessible Rich Internet Applications), DOM (Document Object Model)
Sensory Characteristics: WCAG 1.3.3 (Level A): instructions for understanding and operating content must not rely solely on sensory characteristics such as shape, color, size, visual location, orientation, or sound. For example, "click the round button on the right" is not accessible without additional identification.See also: Perceivable, WCAG (Web Content Accessibility Guidelines)
Skip Navigation: A mechanism allowing keyboard users to bypass blocks of repeated content (such as the header and navigation) and jump directly to the main content. Implemented as a visually hidden link at the top of the page that becomes visible on focus, linking to a main content anchor.See also: Keyboard Navigation, Operable, Focus Indicator
Status Messages: WCAG 4.1.3 (Level AA, added in WCAG 2.1): status messages that inform users of the success or result of an action, a waiting state, or an error must be programmatically determinable through role or property so they can be conveyed by assistive technologies without receiving focus.See also: aria-live, Live Region, Robust
Success Criterion: A specific, testable statement in WCAG that a web page must satisfy to conform to a particular level (A, AA, AAA). WCAG 2.2 contains 87 success criteria across four principles (Perceivable, Operable, Understandable, Robust). Each criterion has associated techniques and understanding documents.See also: WCAG (Web Content Accessibility Guidelines), Conformance Level, Sufficient Techniques
Sufficient Techniques: Implementation methods documented by the W3C that are considered adequate for satisfying a specific WCAG success criterion. Following sufficient techniques is one way to pass a success criterion, but alternative methods may also be acceptable if they produce equivalent results.See also: Advisory Techniques, Success Criterion, WCAG (Web Content Accessibility Guidelines)
SVG Accessibility: Practices for making SVG graphics usable with assistive technologies. Includes adding <title> elements for accessible names, using role="img" for standalone SVGs, providing aria-labelledby for complex graphics, and using role="presentation" for decorative SVGs.See also: Accessible Name, ARIA (Accessible Rich Internet Applications), Alt Text
Switch Access: An assistive technology input method using one or more switches (physical buttons) for users who cannot use a keyboard or touch screen. Switch users navigate by scanning through on-screen options and activating a switch to select. Accessible interfaces must support keyboard operability, which underlies switch access.See also: Motor Disability, Keyboard Navigation, Assistive Technology

T

Tab Order: The sequence in which interactive elements receive keyboard focus when the Tab key is pressed. The tab order should follow a logical, meaningful sequence — typically matching the visual left-to-right, top-to-bottom reading order. An inconsistent tab order is a WCAG 2.4.3 failure.See also: tabindex, Focus Indicator, Keyboard Navigation
tabindex: An HTML attribute controlling the keyboard focus order of elements. tabindex="0" adds an element to the natural tab order. tabindex="-1" removes it from tab order but allows programmatic focus. Positive tabindex values create a custom order and should generally be avoided as they disrupt natural DOM order.See also: Tab Order, Focus Management, Keyboard Navigation
Tagged PDF: A PDF file containing a tag tree that describes the structure of the document content — including headings, paragraphs, images, tables, and reading order. Tags are required for screen readers to correctly parse PDFs. Untagged PDFs are largely inaccessible to assistive technologies.See also: PDF Accessibility, Accessible Document, Screen Reader
TalkBack: Google's built-in Android screen reader that provides spoken, audible, and vibration feedback. TalkBack is preinstalled on Android devices and is the primary screen reader used to test Android app accessibility. It uses gestures for navigation rather than keyboard-based interaction.See also: Screen Reader, VoiceOver, Assistive Technology
Target Size (Minimum): WCAG 2.5.8 (Level AA, added in WCAG 2.2): the size of the target for pointer inputs is at least 24x24 CSS pixels, or spacing of at least 24px from adjacent targets is provided. WCAG 2.5.5 (AAA) requires a minimum target size of 44x44 CSS pixels.See also: Motor Disability, Operable, WCAG 2.2
Text Resize: WCAG 1.4.4 (Level AA): text (except captions and images of text) must be resizable up to 200% without assistive technology and without loss of content or functionality. This requires responsive layouts that do not break when browser font size is increased.See also: Low Vision, Reflow, Perceivable
Text Spacing: WCAG 1.4.12: no loss of content or functionality occurs when users set specific text spacing properties — line height to 1.5x font size, letter spacing to 0.12em, word spacing to 0.16em, and paragraph spacing to 2x font size. Essential for users who require custom spacing for readability.See also: Reflow, Low Vision, Perceivable
Time Limits: WCAG Success Criterion 2.2.1: for content with time limits, users must be able to turn off, adjust, or extend the limit. This protects users with cognitive disabilities, motor disabilities, and anyone who needs more time to complete tasks.See also: Operable, WCAG (Web Content Accessibility Guidelines), Cognitive Disability
Tooltip Accessibility: Tooltips present accessibility challenges because they are typically only shown on hover, excluding keyboard-only users. Accessible tooltips must also appear on focus, remain visible long enough to read, be dismissible without moving focus (WCAG 1.4.13), and not obscure adjacent content.See also: Content on Hover or Focus, Keyboard Navigation, Perceivable
Transcript: A text version of audio or video content that includes all spoken dialogue, sounds, and descriptions of visual information. WCAG requires transcripts for audio-only content (1.2.1) and recommends them for video as an enhanced alternative to captions.See also: Captions, Audio Description, Hearing Impairment

U

Understandable: The third WCAG principle: information and the operation of UI must be understandable. This covers language identification, predictable page behavior, consistent navigation, input assistance (labels, error identification), and helping users avoid and correct mistakes.See also: WCAG Principles (POUR), Plain Language, Error Identification
Undue Burden: A legal standard in US disability law that excuses compliance requirements when implementation would impose significant difficulty or expense. Organizations claiming undue burden must document why accessibility is not reasonably achievable given their resources. It is a high bar rarely met for digital accessibility.See also: Reasonable Accommodation, ADA (Americans with Disabilities Act), Section 508
Unicode and Symbols: Unicode characters used as decorative or functional elements can cause screen reader issues when used inappropriately. Emoji and symbols have verbose descriptions in some screen readers — for example, "face with tears of joy" for the 😂 emoji. Accessible design uses ARIA and HTML semantics rather than Unicode workarounds.See also: Screen Reader, aria-hidden, Perceivable
Universal Design: The design of products and environments usable by all people, to the greatest extent possible, without the need for adaptation or specialized design. The seven principles of universal design include equitable use, flexibility in use, simple and intuitive use, and perceptible information.See also: Inclusive Design, WCAG (Web Content Accessibility Guidelines)
User Agent: Any software that retrieves and renders web content on behalf of users — including browsers, screen readers, media players, and assistive technology. WCAG uses this term to describe the technologies that interpret HTML and CSS. Robust content must work across the full spectrum of user agents.See also: Robust, Assistive Technology, Screen Reader

V

Video Captions: Synchronized text alternatives for the audio content in video, displayed within the video player. WCAG 1.2.2 (AA) requires captions for prerecorded video with audio. Live captions (1.2.4) are required for live video with audio. Captions benefit deaf users, users in noisy environments, and non-native speakers.See also: Captions, Audio Description, Perceivable
Viewport: The visible area of a web page in the browser window. WCAG prohibits using the viewport meta tag to disable user scaling (user-scalable=no) because it blocks pinch-to-zoom on mobile devices — an essential feature for users with low vision.See also: Magnification, Reflow, Low Vision
Visible Focus (2.4.7): WCAG 2.4.7 (Level AA): any keyboard operable user interface must have a mode of operation where the keyboard focus indicator is visible. This ensures keyboard users can track where they are on the page as they navigate. WCAG 2.4.11 (WCAG 2.2) strengthens this by requiring the focused item not be entirely obscured.See also: Focus Indicator, Keyboard Navigation, Operable
Visual Impairment: A broad category including partial vision loss, low vision, color blindness, and total blindness. Web accessibility accommodations vary by type: blind users rely on screen readers; low vision users need text resizing and magnification support; users with color blindness need color-independent information design.See also: Screen Reader, Low Vision, Color Blindness
VoiceOver: The built-in screen reader on Apple devices — macOS, iOS, iPadOS, watchOS, and tvOS. VoiceOver uses gestures on touchscreens and keyboard shortcuts on Mac. It is the primary screen reader for testing Apple platform accessibility and is widely used by blind and low-vision iPhone users.See also: Screen Reader, JAWS (Job Access With Speech), NVDA (NonVisual Desktop Access), TalkBack
VPAT (Voluntary Product Accessibility Template): A standardized template published by the IT Industry Council (ITI) used to document how a product conforms to accessibility standards including WCAG, Section 508, and the European Accessibility Act. A completed VPAT is called an Accessibility Conformance Report (ACR).See also: Accessibility Conformance Report (ACR), Section 508, WCAG (Web Content Accessibility Guidelines)

W

W3C (World Wide Web Consortium): The main international standards organization for the World Wide Web. The W3C develops web standards including HTML, CSS, and WCAG. Its Web Accessibility Initiative (WAI) produces the WCAG guidelines and ARIA specification.See also: WCAG (Web Content Accessibility Guidelines), WAI (Web Accessibility Initiative), ARIA (Accessible Rich Internet Applications)
WAI (Web Accessibility Initiative): The W3C division responsible for developing international accessibility standards and supporting resources. WAI produces WCAG, ARIA, and other accessibility guidance. The WAI website (w3.org/WAI) provides free educational resources including WCAG understanding documents and technique libraries.See also: WCAG (Web Content Accessibility Guidelines), W3C (World Wide Web Consortium), ARIA (Accessible Rich Internet Applications)
WAVE (Web Accessibility Evaluation Tool): A free web accessibility testing tool developed by WebAIM. WAVE provides visual feedback by injecting icons directly into the page to identify errors, alerts, and structural features. Available as a browser extension and API. Best used alongside axe-core for comprehensive coverage.See also: axe-core, Lighthouse, Accessibility Audit
WCAG (Web Content Accessibility Guidelines): The international standard for web accessibility published by the W3C's Web Accessibility Initiative. WCAG 2.2 (2023) is the current version, containing 87 success criteria across three levels (A, AA, AAA) organized under four principles: Perceivable, Operable, Understandable, and Robust.See also: WCAG Principles (POUR), Success Criterion, Conformance Level
WCAG 2.0: WCAG version 2.0 (2008), the foundational version of the modern WCAG guidelines that introduced the four POUR principles and three conformance levels (A, AA, AAA). Still referenced in Section 508 requirements (the 2018 Refresh aligned to WCAG 2.0 AA as the baseline).See also: WCAG (Web Content Accessibility Guidelines), WCAG 2.1, Section 508
WCAG 2.1: WCAG version 2.1 (2018) added 17 new success criteria to WCAG 2.0, addressing mobile accessibility, low vision, and cognitive disability. The additions include 1.3.4 (Orientation), 1.4.10 (Reflow), 1.4.11 (Non-text Contrast), 1.4.13 (Content on Hover or Focus), 2.5.3 (Label in Name), and 4.1.3 (Status Messages).See also: WCAG (Web Content Accessibility Guidelines), WCAG 2.2, Conformance Level
WCAG 2.2: WCAG version 2.2 (September 2023) added 9 new success criteria and deprecated 4.1.1 (Parsing). New criteria include Focus Not Obscured (2.4.11, AA), Focus Appearance (2.4.13, AAA), Consistent Help (3.2.6, A), Redundant Entry (3.3.7, A), and Accessible Authentication Minimum (3.3.8, AA).See also: WCAG (Web Content Accessibility Guidelines), WCAG 2.1, Success Criterion
WCAG 3.0 (Silver): The next generation W3C accessibility guidelines in development, replacing the pass/fail binary model with a multi-dimensional scoring approach. WCAG 3.0 aims to address cognitive disabilities, emerging technologies, and testing consistency more effectively. Still in draft as of 2025.See also: WCAG (Web Content Accessibility Guidelines), WCAG 2.2, WAI (Web Accessibility Initiative)
WCAG Conformance: A claim that a page or set of pages meets all WCAG success criteria at the stated level. A full conformance claim specifies the conformance level, the pages it covers, any relied-upon technologies, any known exceptions, and the WCAG version. Partial conformance is also a recognized claim type.See also: WCAG (Web Content Accessibility Guidelines), Conformance Level, Accessibility Conformance Report (ACR)
WCAG Principles (POUR): The four foundational principles underlying WCAG: Perceivable (information must be presentable in ways users can perceive), Operable (UI must be operable by all users), Understandable (information and UI operation must be understandable), and Robust (content must work with assistive technologies). Often abbreviated as POUR.See also: Perceivable, Operable, Understandable, Robust
Widget Roles: ARIA roles that describe interactive UI widgets — including button, checkbox, combobox, dialog, grid, listbox, menu, radiogroup, slider, spinbutton, switch, tab, and tree. Widget roles define the semantics of complex JavaScript components so assistive technologies can convey their purpose and state.See also: ARIA (Accessible Rich Internet Applications), Landmark Roles, Accessible Name

Z

Zoom: A browser or OS feature that enlarges the entire page or viewport. WCAG 1.4.4 requires text to be resizable to 200% without loss of content or functionality. WCAG 1.4.10 extends this to require reflow at 400% zoom. Websites must not disable browser zoom using viewport meta tags.See also: Magnification, Reflow, Low Vision

Want deeper accessibility insights?

Scan your entire website and generate an official VPAT document — free, in minutes.

Scan Your Site — It's Free