Glossary

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Front-end Development(also: Client-side Development, Front-end Engineering)

The practice of building the user-facing portion of websites and applications using HTML, CSS, and JavaScript. Front-end developers create visual interfaces, handle user interactions, and ensure responsive design across devices. For blind developers, front-end work presents…

Functional Image

An image that serves as an interactive control, such as a link, button, or form input, rather than simply conveying information. When an image is used as a link or button, its alternative text must describe the action or destination rather than the visual content of the image.…

Graceful degradation(also: Graceful degradation)

A design strategy in which web content built with newer or advanced technologies continues to function and remain accessible when those technologies are not supported by a user's browser or assistive technology. Under WCAG 2.0, technologies that are not accessibility-supported…

HTML(also: HyperText Markup Language)

The standard markup language used to create and structure content on the World Wide Web. HTML uses elements (tags) to define the semantic structure of documents, including headings, paragraphs, links, lists, tables, forms, and images. Proper use of semantic HTML is fundamental…

HTML Canvas(also: Canvas API, Canvas Element)

An HTML element used to draw graphics on a web page via JavaScript, rendering content as a bitmap image rather than as structured DOM elements. Unlike SVG, canvas content is not inherently accessible to screen readers because it produces a flat pixel surface with no semantic…

HTML Frame(also: Frame, Frameset, IFrame)

An HTML element that divides a web page into multiple independent sections, each displaying a separate document. Framesets (using the frame and frameset elements) split the browser window into distinct panes, while inline frames (iframe) embed one document within another. Frames…

HTML Table(also: Data Table, Web Table)

An HTML table is a structured element in web markup used to organize data into rows and columns. Tables are created using the table, tr (table row), th (table header), and td (table data) elements. For accessibility, data tables must include proper header markup (th elements…

Heading hierarchy(also: Heading structure, Heading levels)

The logical, nested structure of HTML heading elements (h1 through h6) that organizes web content into a navigable outline. A well-structured heading hierarchy uses heading levels sequentially without skipping levels, with a single h1 for the page title, h2 for major sections,…

Heading hierarchy(also: Heading structure, Heading levels, Document outline)

The logical structure created by using HTML heading elements (h1 through h6) in a nested, hierarchical order to convey the organisation of content on a web page. A proper heading hierarchy starts with a single h1 for the page title, with h2 elements for major sections, h3 for…

Hijax(also: Progressive enhancement with Ajax)

A web development approach coined by Jeremy Keith that applies progressive enhancement principles to Ajax applications. Hijax starts with a fully functional, accessible HTML page and then layers Ajax functionality on top, so that the site degrades gracefully when JavaScript is…

IDE(also: Integrated Development Environment)

A software application that provides a comprehensive environment for writing, testing, and debugging code. Common IDEs include Visual Studio Code, IntelliJ IDEA, and Xcode. In accessibility contexts, IDEs are important because they can host plugins and extensions that help…

Image Map(also: Clickable Map, Imagemap)

An HTML feature that allows different regions of a single image to be designated as separate hyperlinks, each pointing to a different URL. Image maps can be client-side (coordinates and links defined in HTML MAP and AREA elements) or server-side (click coordinates sent to the…

Internationalization(also: i18n)

The process of designing and developing software, websites, or applications so that they can be adapted to different languages, regions, and cultural conventions without requiring engineering changes. Internationalization involves architectural decisions such as supporting…

Internet Archive(also: Wayback Machine, Web Archive)

A non-profit digital library founded in 1996 that archives web pages, books, audio, video, and software for free public access. Its Wayback Machine service stores historical snapshots of websites, allowing researchers to view how web pages appeared at specific points in time. In…

LLM Accessibility(also: AI-Generated Accessibility, Generative AI Accessibility)

The study and practice of how large language models (LLMs) and generative AI tools handle digital accessibility in their outputs, particularly when generating code, user interfaces, or content. Research in this area examines whether LLM-generated code meets accessibility…

Landmarks(also: ARIA Landmarks, Page Landmarks, Landmark Regions)

Designated regions of a web page that provide structural navigation points for assistive technology users. ARIA landmark roles include banner, navigation, main, complementary, contentinfo, search, form, and region. Screen reader users can jump between landmarks using keyboard…

Layout Table(also: Presentational Table)

An HTML table element used to control the visual positioning of content on a web page rather than to present tabular data. Layout tables were a common web design technique before CSS became widely supported, but their use is now considered a significant accessibility barrier.…

Lighthouse(also: Google Lighthouse, Chrome Lighthouse)

An open-source automated tool developed by Google for auditing web page quality, including performance, accessibility, SEO, and progressive web app compliance. Lighthouse runs in Chrome DevTools, as a browser extension, or via command line, and produces scores from 0-100 for…

Linked Data(also: Linked Open Data, LOD)

A method of publishing structured data on the web so that it can be interlinked and queried across different sources using standard web technologies such as URIs and RDF (Resource Description Framework). In accessibility contexts, linked data has been proposed as a way to…

Live Region(also: ARIA Live Region, aria-live)

A section of a web page that is dynamically updated and announced by assistive technologies without requiring the user to navigate to it. Live regions are defined using the WAI-ARIA aria-live attribute, which can be set to "polite" (announced when the screen reader is idle),…

Markup Language

A system of annotations or tags embedded within text that define the structure, presentation, or semantics of content without being displayed as visible text themselves. In web accessibility, markup languages such as HTML, XML, ARIA, and SVG are fundamental because assistive…

Mashup(also: Web mashup)

A web application or page that combines data, functionality, or presentation from two or more external sources to create a new service. Mashups use APIs or data feeds to seamlessly blend content from different sites, often without clear demarcation between sources. In…

MathJax

An open-source JavaScript display engine that renders mathematical notation written in LaTeX, MathML, or AsciiMath in web browsers. MathJax is significant for accessibility because it produces output that can be read by screen readers, supports keyboard navigation of…

MathML(also: Mathematical Markup Language)

An XML-based markup language standardized by the W3C for describing mathematical notation and capturing both its structure and content. MathML enables screen readers and other assistive technologies to interpret and convey mathematical expressions to users with visual…

Metadata

Data that provides structured information about other data or digital content. In accessibility, metadata plays a critical role in describing the accessibility features and characteristics of digital resources — for example, indicating whether a document has alternative text for…

Microservices(also: Microservice Architecture)

A software architecture pattern where an application is composed of small, independent services that communicate over well-defined APIs, each responsible for a specific function and deployable independently. In accessibility tooling, microservices architecture enables modular…

Multilingual Web(also: Multilingual Website, Multi-language Web)

Web content that is available in more than one language, typically through localization of an original website into additional language versions. Multilingual websites present unique accessibility challenges because the localization process can introduce or remove accessibility…

MutationObserver(also: DOM Mutation Observer, Mutation Records API)

An HTML5 browser API that monitors and reports changes to the Document Object Model (DOM) structure of a web page in real time, including additions and removals of elements, attribute changes, and text modifications. For accessibility, MutationObserver is significant because it…

Non-Functional Requirement(also: NFR, Quality Attribute)

A software requirement that specifies how a system should behave rather than what it should do. Non-functional requirements include accessibility, security, performance, maintainability, and usability. In web development, accessibility is a critical non-functional requirement…

Page Segmentation(also: Web Page Segmentation, VIPS)

The process of dividing a web page into distinct visual or structural blocks based on layout cues such as whitespace, borders, colors, and font properties. Page segmentation algorithms like Vision Based Page Segmentation (VIPS) analyze the rendered appearance of pages to…

Progressive Enhancement

A web design strategy that starts with a baseline of essential content and functionality that works in any browser or with any internet connection, then layers on enhanced features for users with more capable browsers or greater bandwidth. Rooted in the "graceful transformation"…

Responsive Design(also: Responsive Web Design, RWD, Mobile First Design)

A web design approach in which layouts, images, and other content elements adapt fluidly to the size and capabilities of the user's device, providing an optimal viewing experience across desktops, tablets, and mobile phones without requiring separate versions of a site.…

Rich Internet Application(also: RIA, Dynamic Web Application)

A web application that uses JavaScript and related technologies to provide interactive features, dynamic content updates, and sophisticated user interface widgets that approach the functionality of desktop applications. RIAs present significant accessibility challenges because…

Rich Text(also: Formatted Text, Styled Text)

Text content that includes visual formatting attributes beyond plain characters, such as font size, font family, color, bold, italic, underline, and other styling properties. On the web, rich text is created through HTML elements and CSS properties that give text visual emphasis…

Rich internet application(also: RIA)

A web application that uses client-side scripting (typically JavaScript) to provide dynamic, interactive functionality similar to desktop software, including features like drag-and-drop, real-time updates, and complex widgets. Rich internet applications present significant…

Scalable Vector Graphics(also: SVG)

An XML-based vector image format for two-dimensional graphics that supports interactivity and animation. Unlike bitmap formats (JPEG, PNG, GIF) which store images as grids of pixels, SVG describes shapes, paths, and text mathematically, allowing images to scale without loss of…

Search Engine Accessibility(also: Accessible Search)

The usability and accessibility of search engine interfaces and results for people with disabilities, particularly blind and visually impaired users who interact via screen readers. Search engines present unique accessibility challenges because their interfaces combine complex…

Search Engine Optimization(also: SEO)

Search engine optimization (SEO) is the practice of improving a website's visibility and ranking in search engine results through techniques such as using descriptive page titles, meaningful headings, alt text for images, descriptive link text, and structured markup. Many SEO…

Semantic Abstraction

The practice of defining interface elements, content, or interactions by their meaning and purpose rather than their specific visual or physical presentation. In accessibility, semantic abstraction is a foundational principle — semantic HTML elements like nav, main, and button…

Semantic Description(also: SD, Navigational Semantic Description)

A formal representation of the meaningful structure and navigational relationships within a complex document component such as an HTML table, frame, or XML fragment. Semantic descriptions capture what groups of content mean and how they relate to each other, going beyond…

Semantic Enrichment(also: Semantic Annotation, Semantic Markup Enhancement)

Semantic enrichment is the process of adding meaningful structural and contextual information to content that may lack it in its original representation. In the context of web accessibility, this often involves augmenting presentation-oriented markup with data attributes or…

Shadow Page(also: Shadow Site, Text-Only Alternative)

A separate, simplified version of a web page created specifically to meet accessibility requirements, typically offering a text-only or reduced-complexity version of the original content. While shadow pages can address some accessibility barriers, they are generally considered a…

Single Page Application(also: SPA)

A web application architecture that dynamically updates page content in response to user interactions without requiring a full page reload, instead using JavaScript to modify the Document Object Model (DOM) and fetch data asynchronously. SPAs present unique accessibility…

Single-Page Application(also: SPA)

A web application that loads a single HTML document and dynamically updates its content through JavaScript without requiring full page reloads. SPAs use client-side routing and AJAX requests to fetch data and render new views within the same page, creating a more fluid,…

Syntactic Accessibility(also: Technical Accessibility)

The dimension of web accessibility concerned with the correctness of code sent to the browser and assistive technologies. Syntactic accessibility focuses on whether HTML markup, ARIA attributes, and other technical elements conform to standards so that content can be properly…

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.…

Table Linearization(also: Table Serialization)

Table linearization is the process of converting a two-dimensional HTML table into a one-dimensional sequence of text for non-visual presentation. When a screen reader linearizes a table, it reads the content cell by cell, row by row, from top-left to bottom-right, stripping…

Text-Mode Browser(also: Text Browser, Terminal Browser, Console Browser)

A web browser that renders web pages as text only, without displaying images or graphical layout, typically running in a command-line terminal or console environment. The most well-known text-mode browser is Lynx, developed at the University of Kansas in the early 1990s.…

Transformation Proxy(also: Transcoding Proxy, Web Accessibility Proxy)

A transformation proxy is an intermediary server that sits between a user and the web, intercepting web pages and modifying their content before delivering them to the user's browser. In accessibility contexts, transformation proxies are used to improve the accessibility of web…

Unicode(also: Unicode Standard, UTF-8)

A universal character encoding standard that assigns a unique code point to every character in every writing system, enabling consistent representation and processing of text across all platforms, programs, and languages. Unicode is foundational to digital accessibility because…