Glossary

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Accessibility Baseline(also: Baseline, Technology Baseline, WCAG Baseline)

An accessibility baseline, as used in WCAG 2.0 and later versions, is the set of technologies that a content author assumes are supported and enabled in the user agents (browsers and assistive technologies) used by their target audience. Authors must ensure that all content…

Accessibility Conformance Level(also: WCAG Conformance Level, Conformance Level)

Accessibility conformance levels are the tiered ratings defined by the Web Content Accessibility Guidelines (WCAG) to indicate the degree to which web content meets accessibility success criteria. WCAG defines three levels: Level A (minimum, addressing the most critical…

Accessibility-supported(also: Accessibility supported technology)

A WCAG 2.0 concept describing a web technology that has sufficient support from user agents (browsers) and assistive technologies to reliably convey accessibility information to users with disabilities. For a technology to be considered accessibility-supported, it must contain…

Accessible Authentication(also: WCAG 3.3.7, Accessible Authentication (Minimum))

A web accessibility requirement introduced in WCAG 2.2 (Success Criterion 3.3.7) that mandates for each step in an authentication process relying on a cognitive function test — such as remembering a password, solving a puzzle, or transcribing distorted text — at least one…

Alternative Text(also: Alt Text, Alt Attribute)

Text associated with an image that serves the same purpose and conveys the same essential information as the image. Alternative text is a fundamental web accessibility requirement specified in WCAG, enabling screen reader users to understand image content. Standards for writing…

Checkpoint(also: WCAG Checkpoint, Success Criterion, Accessibility Checkpoint)

A checkpoint is a specific, testable accessibility requirement in a set of guidelines — for example, 'provide a text equivalent for every non-text element' is WCAG 1.0 checkpoint 1.1. The term is strongly associated with WCAG 1.0, which was organised into 65 numbered checkpoints…

Conformance Level(also: WCAG Level, Priority Level)

The three-tiered classification system used by WCAG to rank success criteria by their importance and impact on accessibility. Level A represents the minimum baseline — criteria that must be met or some users will be completely unable to access content. Level AA addresses the…

Contrast Ratio(also: Color Contrast Ratio, Luminance Contrast Ratio)

A numerical measure of the difference in perceived brightness between two colors, expressed as a ratio ranging from 1:1 (no contrast) to 21:1 (maximum contrast, black on white). WCAG 2.2 requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text (Level…

Epilepsy(also: Seizure Disorder)

A chronic neurological condition characterized by recurrent, unprovoked seizures caused by abnormal electrical activity in the brain. Epilepsy affects roughly 1% of the population globally and spans a wide range of seizure types and severities, with some people experiencing…

Extended Audio Description(also: Extended AD, Paused Audio Description)

A form of audio description in which the video is temporarily paused to allow time for a longer, more detailed description of visual content before resuming playback. Extended AD is used when gaps between dialogue are too short to convey all essential visual information through…

Flashing Content(also: Flashing, Flash)

Visual content that alternates between contrasting states at a rate that can trigger seizures in people with photosensitive epilepsy. WCAG defines a flash as a pair of opposing luminance changes or a transition involving saturated red. Content with more than three flashes per…

Focus Indicator(also: Focus Ring, Visible Focus, Focus Outline)

A visual cue that shows which interactive element on a page or in an application currently has keyboard focus. Focus indicators are typically rendered as an outline, border, or highlight around the focused element. They are essential for keyboard users and screen magnification…

Inline Audio Description(also: Standard Audio Description, Inline AD)

The standard form of audio description where narrated descriptions of visual content are inserted into natural pauses in dialogue and sound during video playback, without pausing the media. Inline AD must fit within available gaps, which limits the amount of detail that can be…

Interface Consistency(also: Consistent Navigation, Consistent Identification, UI Consistency)

Interface consistency is a design principle requiring that navigational mechanisms, visual layouts, and interactive components appear and behave in the same way across different pages, screens, or applications. In accessibility, consistency is critical because users who rely on…

Link Purpose(also: Link Purpose (In Context), WCAG 2.4.4, Link Text)

A WCAG 2.4.4 Level A success criterion requiring that the purpose of each link be determinable from the link text alone, or from the link text together with its programmatically determined context (surrounding sentence, list item, table cell, containing paragraph). Links worded…

Long Description(also: Extended Description, longdesc)

A detailed textual description of an image or other non-text content that goes beyond the brief summary provided by alt text. Long descriptions are used for complex images such as charts, diagrams, infographics, or detailed illustrations where a short alt text cannot convey all…

On Input(also: WCAG 3.2.2)

WCAG 2.1 success criterion 3.2.2 (Level A) requires that changing the setting of any user interface component does not automatically cause a change of context (e.g., submitting a form, navigating to a new page, or moving focus to another component) unless the user has been…

POUR Principles(also: POUR, Four Principles of Accessibility)

The four foundational principles of the Web Content Accessibility Guidelines (WCAG): Perceivable, Operable, Understandable, and Robust. Perceivable means information must be presentable in ways users can perceive (e.g., alt text for images, captions for video). Operable means…

Perceivability(also: Perceivable)

The quality of information or interface elements being detectable through one or more senses — sight, hearing, or touch. Perceivability is the first principle of WCAG 2.0 and requires that information and user interface components be presentable to users in ways they can…

Sensory Characteristics(also: WCAG 1.3.3, Success Criterion 1.3.3)

WCAG 2.1 Success Criterion 1.3.3 (Level A), which requires that instructions for understanding and operating content not rely solely on sensory characteristics such as shape, colour, size, visual location, orientation, or sound. Examples that violate 1.3.3 include referring to…

Success Criteria(also: Success Criterion, SC)

The testable statements within the Web Content Accessibility Guidelines (WCAG) that define specific requirements for making web content accessible. Each success criterion is assigned a conformance level (A, AA, or AAA) indicating its priority. Success criteria are…

Sufficient Techniques(also: Sufficient Advisory Techniques)

In the WCAG framework, sufficient techniques are documented methods for meeting a specific success criterion. If a content author correctly implements a sufficient technique, it is enough to satisfy the associated requirement. Multiple sufficient techniques may exist for a…

Tab Order(also: Focus Order, Navigation Order, Tabbing Order)

The sequence in which interactive elements receive keyboard focus when a user presses the Tab key to navigate through a web page or application. A logical tab order follows the visual layout and task workflow, allowing keyboard-only users to interact with content efficiently.…

Text Alternative(also: Alt Text, Alternative Text, Text Equivalent)

A textual replacement for non-text content, primarily images, that conveys the same purpose or information as the visual element. Text alternatives are essential for users who cannot perceive images, including people who are blind or have low vision and rely on screen readers.…

Text Alternatives(also: Text Alternative, Text Equivalent)

WCAG 2.1 Guideline 1.1 and success criterion 1.1.1 require that all non-text content (images, charts, audio, video, form controls, etc.) have a text alternative serving the equivalent purpose. Text alternatives can be presented as alt text on an image, an aria-label on a…

Text Reflow(also: Content Reflow, Responsive Text)

The ability of text content to rearrange and wrap within its container when the viewport is resized or text is zoomed, so that users can read without horizontal scrolling. Text reflow is essential for users with low vision who magnify content, as well as for mobile users on…

Time-Based Media(also: Multimedia Content, Synchronized Media)

Content that unfolds over time, including audio, video, audio-video combinations, and interactive multimedia presentations. WCAG Guideline 1.2 requires that time-based media be made accessible through alternatives such as captions for the deaf and hard of hearing, audio…

Touch Target Size(also: Tap Target Size, Target Size)

The physical area of an interactive element on a touchscreen that responds to user input. Adequate touch target sizing is critical for accessibility, particularly for users with motor impairments who may have difficulty precisely tapping small areas. WCAG 2.2 Success Criterion…

Transcripts(also: Transcript, Text Transcript)

A written, text-based representation of spoken audio or audiovisual content. WCAG 2.1 success criterion 1.2.1 (Audio-only and Video-only Prerecorded) requires an alternative for time-based media — typically a transcript — for pre-recorded audio-only content such as podcasts,…

Understandability(also: Understandable, Comprehensibility)

The quality of information or interface elements being cognitively accessible — meaning a user can not only perceive the content but also internalise its meaning and know how to act on it. Understandability is one of the four principles of WCAG 2.0, requiring that information…

WCAG 2.4 Navigable(also: Guideline 2.4, Navigable Guideline)

A guideline within the Web Content Accessibility Guidelines (WCAG) under the Operable principle that requires web content to provide ways to help users navigate, find content, and determine where they are. Its success criteria address bypass blocks (skip navigation links), page…

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