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Accessibility terms

25 accessibility terms, defined plainly and cross-referenced.

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Accessibility (a11y)AccessibilityAccessibility (often shortened to a11y for the 11 letters between the A and the Y) means designing and building digital products that people of all abilities can perceive, understand, navigate, interact with, and contribute to. It is not a feature tier or a special mode. It is a fundamental property of well-built software, no different from security or performance.Accessibility AuditAccessibilityAn accessibility audit is a systematic evaluation of a website, application, or digital product against accessibility standards (typically WCAG 2.2 AA). It combines automated scanning (axe-core, WAVE), manual testing (keyboard, screen reader), expert review, and sometimes user testing to produce a comprehensive list of issues and remediation guidance.Accessibility OverlayAccessibilityAn accessibility overlay is a third-party script (typically JavaScript) that a website operator adds to their site, claiming it will automatically detect and fix accessibility problems and/or add a toolbar of accessibility settings. Overlays are widely condemned by the disability community and accessibility professionals. They cannot make a site accessible, often introduce new barriers, and in some cases increase legal liability. The W3C Overlay Fact Sheet, signed by over 1,000 experts, explains why.Accessible FormsAccessibilityAccessible forms are form controls that every user can perceive, understand, and complete. This means every input has a visible and programmatically associated label, clear error messages, logical focus order, and sufficient touch or click target sizes. Poorly built forms are one of the most common barriers on the web and a frequent source of WCAG violations.ADA ComplianceAccessibilityADA compliance in the digital context means ensuring a website or mobile application meets the accessibility requirements of the Americans with Disabilities Act (ADA). While the ADA predates the commercial internet, courts and the Department of Justice have consistently held that websites are places of public accommodation and must be accessible to people with disabilities, using WCAG as the technical benchmark.Alt TextAccessibilityAlt text (alternative text) is the text description embedded in an image's HTML alt attribute that screen readers announce in place of the image. It is the single most important accessibility technique for images. Good alt text conveys the content and function of an image. Bad alt text (or missing alt text) is a WCAG Level A failure and one of the most common accessibility defects on the web.ARIAAccessibilityARIA (Accessible Rich Internet Applications) is a W3C specification that supplies the semantics missing in plain HTML for interactive widgets and dynamic content. ARIA attributes such as role, aria-label, aria-expanded, and aria-live tell assistive technologies what elements are and what they do. The first rule of ARIA: if you can use a native HTML element that already has the semantics built in, do that instead.axe-coreAccessibilityaxe-core is an open-source accessibility testing engine developed by Deque Systems. It is the industry-standard library for automated accessibility testing, integrated into browsers, CI/CD pipelines, and testing frameworks. axe-core runs a set of rules against a page's DOM and reports violations with WCAG success criterion mappings, element selectors, and fix guidance.

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Captioning / TranscriptsAccessibilityCaptions are synchronised text that displays spoken dialogue, sound effects, and other audio information during video playback. Transcripts are full-text records of audio or video content. Both are WCAG Level A requirements for pre-recorded multimedia. Captions serve people who are deaf or hard of hearing, non-native speakers, and anyone watching without sound.Color Contrast RatioAccessibilityColor contrast ratio measures the difference in luminance between foreground text and its background, expressed as a ratio (e.g., 4.5:1). WCAG requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text (18px bold or 24px regular) at Level AA. Low contrast is the most common accessibility failure on the web, affecting users with low vision and everyone in bright sunlight.

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European Accessibility Act (EAA)AccessibilityThe European Accessibility Act (EAA, Directive 2019/882) is an EU directive requiring that key digital products and services be accessible to people with disabilities. It came into full effect on June 28, 2025, and applies to any organisation operating in or targeting the EU market, regardless of where the company is headquartered.

Focus Management / Focus IndicatorAccessibilityFocus management is the practice of programmatically moving keyboard focus between elements when the UI changes (e.g., opening a dialog, loading new content, revealing a menu). A focus indicator is the visible highlight or outline around the element that currently has keyboard focus. Both are critical for keyboard and screen reader users. WCAG 2.2 introduced Focus Not Obscured (AA) and Focus Appearance (AAA) to strengthen requirements.

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Heading HierarchyAccessibilityHeading hierarchy is the practice of using <h1> through <h6> elements in a logical, nested order that reflects the content structure of the page, just like the outline of a book or report. Headings must not skip levels, and a page should have exactly one <h1>. Heading hierarchy is critical for screen reader navigation, SEO, and general content comprehension.High Contrast ModeAccessibilityHigh Contrast Mode is an operating system accessibility setting that replaces the colour scheme on screen with a high-contrast palette (typically black and white or black and yellow) to improve readability for users with low vision, colour blindness, or light sensitivity. The CSS prefers-contrast media query lets websites detect and respond to this preference.

Inclusive DesignAccessibilityInclusive design is a design methodology that considers the full range of human diversity (ability, language, culture, gender, age) from the outset, rather than designing for a narrow "average" user and then retrofitting for everyone else. It is a broader, more proactive frame than accessibility compliance, though the two deeply overlap.

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Keyboard NavigationAccessibilityKeyboard navigation means all interactive functionality on a web page can be operated using only a keyboard, without requiring a mouse, touch, or other pointing device. Tab moves focus between focusable elements, Enter and Space activate controls, and arrow keys navigate within composite widgets. Keyboard accessibility is a WCAG Level A requirement and a prerequisite for many assistive technologies.

Landmark ElementsAccessibilityLandmark elements are HTML5 semantic elements that define the major regions of a page (<header>, <nav>, <main>, <aside>, <section>, <footer>). They create navigation points that screen reader users can jump to directly, bypassing repetitive content and moving between page regions with a single keystroke.

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Readability (Flesch Reading Ease)AccessibilityReadability measures how easy a text is to read and understand. The Flesch Reading Ease test scores text from 0 (very hard) to 100 (very easy) based on sentence length and syllable count. WCAG recommends a Flesch-Kincaid Grade Level of 9 or lower (plain English) for web content, though specialised content may require higher levels.Reduced MotionAccessibilityReduced motion is an accessibility setting that allows users to disable or minimise animations, transitions, and parallax effects in software. The CSS prefers-reduced-motion media query lets websites detect this preference and serve static alternatives. Excessive motion can cause disorientation for users with vestibular disorders and trigger seizures. WCAG requires that moving content can be paused, stopped, or hidden.

Screen ReaderAccessibilityA screen reader is a software application that converts digital text and interface elements into synthesised speech or braille output. It is the primary assistive technology used by people who are blind or have low vision to navigate computers, websites, and mobile devices. Popular screen readers include JAWS, NVDA, VoiceOver (Apple), and TalkBack (Android).Section 508AccessibilitySection 508 is a US federal law requiring that all information and communication technology (ICT) developed, procured, maintained, or used by the federal government be accessible to people with disabilities. It amended the Rehabilitation Act of 1973 and was updated in 2017 to adopt WCAG 2.0 Level AA as the technical standard.Semantic HTMLAccessibilitySemantic HTML means using HTML elements according to their intended meaning (<nav> for navigation, <h1> through <h6> for headings, <button> for buttons), rather than styling generic elements to look like something they are not. Semantic HTML is the foundation of web accessibility because it tells browsers, search engines, and assistive technologies what each part of the content actually is.

Touch Target SizeAccessibilityTouch target size is the minimum dimension of interactive elements on touchscreen devices. WCAG 2.2 introduced Target Size (Minimum) as a Level AA requirement: pointer targets must be at least 24 by 24 CSS pixels, with exceptions for inline links, equivalent targets, and essential controls.

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WAVE ToolAccessibilityWAVE (Web Accessibility Evaluation Tool) by WebAIM is a free browser extension and online tool that visually overlays accessibility issue indicators directly on the page. It provides an intuitive, visual approach to accessibility auditing, displaying icons for errors, alerts, and ARIA features directly on the web page for fast identification.WCAG (2.1, 2.2)AccessibilityThe Web Content Accessibility Guidelines (WCAG) are the internationally recognised technical standard for making web content accessible to people with disabilities. Published by the W3C Web Accessibility Initiative (WAI), WCAG 2.2 is the latest stable version, adding nine new success criteria on top of WCAG 2.1 with a focus on mobile accessibility, cognitive load reduction, and authentication barriers.

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