WCAG Glossary

(Note: Sourcing for much of this glossary comes from W3C’s Web Accessibility Initiative (WAI).


Accessible video: Avoiding flashing, planning for sign language and captioning, and incorporating visual descriptions.

Accessible audio: Avoiding distracting sounds and ensuring clear speaking so captioners can accurately report what’s being said.

Accessibility supported: Works with users’ assistive technologies as well as the accessibility features in browsers and other user agents.

American Sign Language (ASL): A complete, natural language that has the same linguistic properties as spoken languages with grammar that differs from English. ASL is expressed by movements of the hands and face. 

Assistive technology (AT): Any item, piece of equipment, software program, or product that helps to increase or maintain the ability of people with disabilities to perform different activities and live independently. (See also W3C-WAI.)

Audio description: Narration added to a soundtrack to describe important visual details that cannot be understood from the main soundtrack alone.

Automated scan: Software that automatically detects accessibility issues.


Blocks of text: More than one sentence of text, for example a paragraph, which also helps to organize content on a web page.

Braille: Reading system using six to eight raised dots in various patterns to represent letters and numbers. The characters are read by scanning over the raised dots using the fingertips. Braille is used by people who are blind, but not all individuals who are blind know braille.

Breadcrumb trail: Shows the locations in the path a user took to reach a particular Web page. This helps the user understand how content has been structured and how to navigate back to where they were on a website. 

Button: An element that links to website pages, sections, external links, form submission or other content.


CAPTCHA: Security technique that requires a user to input a distorted set of characters from an image to access a web page or function.

Captions: Words displayed on televisions, computers, mobile devices, or movie screens that describe the audio or sound portion of a program or video. They allow viewers who are deaf or hard-of-hearing to follow the dialogue and the action of a program simultaneously.

Changes in context: Changes that, if made without a user knowing, can disorient users who are not able to view the entire page simultaneously. Changes in context include changes of user agent, viewport, focus and content that changes the meaning of the Web page.

Contrast ratio: A measure of the difference in perceived luminance or brightness between two colors. WCAG Success Criteria 1.4.3, 1.4.6 and 1.4.11 all cover this.

CSS pixel: Canonical unit of measure for all lengths and measurements in CSS used to add elements such as font and color.

Content: All information in a web page or application, including images, videos, and audio, in addition to alt text, scripts, and code or markup that defines how content is organized and presented. 

Context-sensitive help: Help text that provides information related to the function being performed. Clear labels can act as context-sensitive help.


Digital asset: Anything that exists in a digital format, including websites, documents, emails, images, mobile apps, and software products.

Down-event: Platform event that occurs when the trigger stimulus of a pointer is depressed. The down-event may have different names on different platforms such as “touchstart” or “mousedown”.

Dyscalculia: Learning difficulty that affects an individual’s ability to do basic arithmetic such as addition, subtraction, multiplication, and division.

Dyslexia: Learning difficulty characterized by problems with word recognition, spelling and reading comprehension. 


Electronic information technology (EIT): Term used in the 1998 amendments to Section 508 of the Rehabilitation Act  to refer to the scope of products covered under Section 508. Section 508 requires that electronic and information technology that is developed, procured, maintained, or used by the federal government be accessible.

Essential: Something that If removed, would fundamentally change the information or functionality of the content, and that information and functionality cannot be achieved in another way that would conform. For example, a banking app may require that a check be scanned only in landscape mode in order to be successfully deposited. 


Focus indicator: Often just a blue line or highlighted box around a link or a form or text field that makes clear where you are on a web page.

Form controls: Objects that users interact with, such as drop-downs, checkboxes, and text fields. Form controls must be properly labeled so that users understand the purpose of the control. 

Form validation: Feedback that lets a user know if they filled out a form with the necessary information and in the correct way.

Functionality: All actions a user may initiate on a website including navigating, searching for information, making a reservation, making a purchase, and accessing services.


General flash: Defined by “a pair of opposing changes in relative luminance of 10% or more of the maximum relative luminance where the relative luminance of the darker image is below 0.80; and where “a pair of opposing changes” is an increase followed by a decrease, or a decrease followed by an increase, and a red flash is defined as any pair of opposing transitions involving a saturated red.”

GitHub: A central host of repositories, along with wiki documentation, pull request management and issue tracking. Several W3C groups use GitHub infrastructure for specification and test authoring workflows.


Heading: Helps organize content on a web page. Also used by browsers, plug-ins, and assistive technologies to navigate Web pages.

Human language: Language that is spoken, written or signed [through visual or tactile means] to communicate with humans. See also sign language.


Input devices: Computer hardware such as a keyboard, mouse, webcam, and microphone that sends data.

Input element: A typed data field, usually with a form control to allow the user to edit the data.

Input error: Information provided by the user that is either in a wrong format or not input at all.


JAWS: Computer screen reader program that enables users who are blind or visually impaired to engage with the content on the screen either with a text-to-speech output or by a refreshable Braille display.


Keyboard interface: Software that lets users apply a keystroke even when there’s no actual keyboard. Many mobile devices have keyboard interfaces within their operating system as well the option to connect external wireless keyboards

Keyboard shortcut: Ctrl+C, Crtl+X, Crtl+V, etc. are examples of shortcuts that allow a user to take an action they’d often perform with a mouse.


Label: A visible or hidden descriptive name given to checkboxes, drop-down menus, controls, dialogs, and other website features so the user can understand their purpose. A label is presented to all users while the name may only be exposed by assistive technology.

Landmark: Identifies sections of a page so users, especially those using assistive technology, can know where they are on a web page. This helps them better navigate and skip over blocks of content.

Language of parts: A WCAG Success Criterion which ensures that the language in different sections of a website is identified so that different types of assistive technologies can pronounce them correctly and know, for example, if they should be reading from L to R or R to L.

Large scale: Font that is at least 18 pt. or 14 pt. when bold.

Link purpose: Nature of the result obtained by activating a hyperlink. The user should be able to understand a link’s purpose from its text. 


Mechanism: Method for achieving a result. For example, people who navigate sequentially through content benefit from a mechanism that lets them skip over blocks of content that are repeated on every page, such as navigation links, heading graphics, and advertising frames. 

Metadata: “Data about data,” or data that offers the context in which information and data should be interpreted. Answers questions about data (who, what, how, why, etc.) so the meaning of data can be better understood. 

Multiple ways: Providing a user more than one way to get to the information they’re seeking on a website. This can include the search function, a glossary, a sitemap and links on webpages that lead to more information.


Navigation order: The order in which a user navigates through a website using a keyboard.

Neurodiversity: Refers to how our unique brains process information and interact with our environment in often very different ways. Frequently used in connection to autism.

Non-text content: Any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language, for example graphs, images and audio and visual content.


Operable: One of the four principles of accessibility. Users must be able to operate the interface, meaning the interface cannot require interaction that a user cannot perform.

Orientation: The direction in which content is presented on a screen, for example portrait or landscape. What’s important is that content’s orientation is never restricted to one or the other so that it always matches the device display orientation.


Paused: Stopped by user request and not resumed until requested by user.

Perceivable: Users must be able to perceive the information being presented. It can’t be inaccessible to all of their senses.

Pointer input: Ways of engaging functionality on a digital asset, with  for example, a mouse pointer, a finger interacting with a touch screen, an electronic pencil/stylus, or a laser pointer.

Programmatically determined: Determined by software from author-supplied data provided in a way that different user agents, including assistive technologies, can extract and present this information to users in different modalities.

Purely decorative: Serving only an aesthetic purpose, providing no information, and having no functionality.


Red flash: Any pair of opposing transitions involving a saturated red. A pair of opposing changes in relative luminance that can cause seizures in some people if it is large enough and in the right frequency range.

Real-time event: Event that occurs at the same time as the viewing and is not completely generated by the content. For example, a Webcast of a live performance or people bidding in an on-line auction.

Reasonable accommodation: Any modification or adjustment to a job or the work environment that will enable an applicant or employee with a disability to participate in the application process or to perform essential job functions.

Refreshable Braille: Mechanical terminal that displays a line of Braille characters (usually 40-80) by raising and lowering the dots (pins) dynamically. It changes as the user moves the cursor around on the screen, using either the command keys, cursor routing keys, or Windows and screen reader commands.

Region: Perceivable, programmatically determined section of content. In HTML, any area designated with a landmark role would be a region.

Relationships: Meaningful associations between distinct pieces of content.

Relative luminance: The relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white.

Robust content: Compatible with different browsers, assistive technologies, and other user agents.


Same functionality: Having the same result when used. For example, a submit “search” button on one Web page and a “find” button on another may both have a field to enter a term and list topics in the web site related to the term submitted.

Section: Self-contained portion of written content that deals with one or more related topics or thoughts. A section may consist of one or more paragraphs and include graphics, tables, lists, and sub-sections.

Screen readers: Software programs that allow blind users or users with visual impairments to read the text that is displayed on the computer screen with a speech synthesizer or braille display.

Sign language: Language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning.

Single pointer: Input that operates with one point of contact with the screen, for example single taps and clicks, double-taps and clicks, long presses, and path-based gestures.

Speech recognition: Recognizing words for speech-to-text (STT) transcription, virtual assistants, and other speech user interfaces. (Note this is distinct from voice recognition.)

Style property: Property whose value determines the presentation (e.g. font, color, size, location,) of content elements as they are rendered (e.g. on screen, via loudspeaker or via braille display) by user agents.

Supplemental content: Additional content that illustrates or clarifies the primary content, for example, an audio version of a Web page.

Synchronized captions: Unlike typical captions where chunks of words show on the screen all at once, words show at the same time the speaker is saying them.


Target: Region of the display that will accept a pointer action, such as the interactive area of a user interface component.

Text alternative (also “Alt text”): Text that is programmatically associated with non-text content such as charts or images so that the non-text content can be described by a screen reader. Not used for images that are purely decorative and have no meaning.

Text labels: These controls have a visual label, as well as a programmatic label, known as its Accessible Name. Users have a much better experience if the visible text labels of controls match their accessible names.


Understandable: One of the four principles of accessibility according to WCAG, means that content is predictable and easy to grasp by the widest audience possible.

Universal design: Process of creating products that are usable by people with the widest possible range of abilities, operating within the widest possible range of situations. “Accessibility” on the other hand refers to design for people with disabilities.

User agent: Browsers, browser extensions, media players, readers and other applications that render web content.

User inactivity: Any continuous period of time where no user actions occur. The method of tracking is determined by the website or application.

User Interface component: A part of the content that is perceived by users as a single control for a distinct function. For example, a user interface control might let a user know that they need to indicate where they live or their date of birth.  

User controllable: Data that is user-viewable and that the user can change and/or delete through an intentional action, for example, updating an address or phone number.


Viewport: The viewing area in which content can be seen. 

Visual focus:Helps a person know which element among multiple elements has the keyboard focus. A keyboard focus indicator can take different forms. One common form is a caret within the text field to indicate that the text field has the keyboard focus. 

Visually customizable: Font, size, color, and background can be set by the user.


WAI-Accessible Rich Internet Applications Suite (ARIA): A suite of web standards that define how to make web content and applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with HTML, JavaScript, and related technologies. 

WAVE: One of several web accessibility evaluation tools which are software programs or online services that help you determine if web content meets accessibility guidelines.

WCAG conformance: Meeting the requirements of WCAG success criteria. There are five requirements that must be met, including fully meeting at least one level of conformance.

Web accessibility: Ensuring that websites, electronic documents and other digital information can be independently accessed and used by people with disabilities, including by those who use assistive technology.