Reference
Accessibility Glossary
Plain-language definitions of the terms Shopify merchants encounter when working on accessibility compliance. Every term is linked to the canonical W3C / DOJ / EU primary source.
Alt text (alternative text)
Alt text is a written description of an image that screen readers announce to people who cannot see the image, and that search engines use to understand image content.
WCAG (Web Content Accessibility Guidelines)
WCAG is the international standard for web accessibility, published by the W3C, organized into 50+ testable success criteria across four principles: perceivable, operable, understandable, and robust.
Screen reader
A screen reader is assistive software that converts on-screen content into synthesized speech or refreshable braille, enabling blind and low-vision users to navigate websites, apps, and documents.
ADA (Americans with Disabilities Act)
The ADA is the 1990 US federal civil-rights law that prohibits discrimination on the basis of disability; Title III applies to public accommodations including ecommerce websites.
EAA (European Accessibility Act)
The EAA (Directive 2019/882) is the European Union accessibility law requiring ecommerce services sold to EU consumers to meet WCAG 2.1 + 2.2 AA; enforcement began 28 June 2025.
Accessibility overlay
An accessibility overlay is a JavaScript widget that injects accessibility "fixes" at runtime without modifying source code; the DOJ and disability advocates do not consider overlays sufficient for ADA compliance.
Accessibility statement
An accessibility statement is a public-facing page declaring a website's conformance with accessibility standards, known limitations, and a contact mechanism for users to report issues.
Color contrast
Color contrast is the luminance ratio between text and its background; WCAG 2.1 AA requires at least 4.5:1 for body text and 3:1 for large text.
Keyboard navigation
Keyboard navigation is the ability to operate every interactive part of a website using only the keyboard — Tab, Shift+Tab, Enter, Space, Arrow keys, and Escape — without requiring a mouse.
Focus indicator
A focus indicator is the visible outline or styling that shows which element currently has keyboard focus, typically a 2-3px outline drawn by the browser.
Compliance score
A compliance score is the percentage of WCAG success criteria a website passes, typically calculated as `passed_criteria / total_criteria * 100`.
Section 508
Section 508 is the US federal law requiring electronic and information technology developed, procured, maintained, or used by federal agencies to be accessible to people with disabilities. The Section 508 standards were updated in 2017 to align with WCAG 2.0 AA.
VPAT (Voluntary Product Accessibility Template)
A VPAT is a standardized document, published by the Information Technology Industry Council (ITI), that vendors use to declare a product's conformance with Section 508 / WCAG accessibility standards.
AODA (Accessibility for Ontarians with Disabilities Act)
AODA is the Ontario provincial law (Statutes of Ontario, 2005, Chapter 11) that mandates accessibility for organizations doing business in Ontario, with WCAG 2.0 AA as the technical standard for digital content.
ADA demand letter
An ADA demand letter is a pre-litigation notice from a plaintiff (often via a serial-plaintiff law firm) alleging that a website violates ADA Title III and demanding remediation plus a settlement payment, typically within 30-60 days.
Serial plaintiff
A serial plaintiff is an individual who files large numbers of ADA Title III lawsuits — typically through a small group of plaintiff law firms specializing in disability-rights litigation.
ADA Title III
ADA Title III is the section of the Americans with Disabilities Act (42 U.S.C. §§ 12181-12189) that prohibits discrimination on the basis of disability by private entities operating "places of public accommodation" — including, per US case law, commercial websites.
Unruh Civil Rights Act
California's Unruh Civil Rights Act (Civil Code §§ 51-51.3) prohibits business establishments from discriminating against disabled persons and is the state-law vehicle most often paired with ADA Title III claims in California ecommerce-accessibility cases.
Skip link
A skip link is a hidden-by-default link at the top of a page that becomes visible when keyboard-focused, allowing keyboard and screen-reader users to bypass repetitive navigation and jump straight to the main content.
ARIA landmark
ARIA landmarks are HTML5 semantic elements (`<header>`, `<nav>`, `<main>`, `<aside>`, `<footer>`, `<form>`) and their `role=` equivalents that map to navigable page regions for screen-reader users.
Empty alt attribute (`alt=""`)
An empty `alt` attribute (`alt=""`) on an `<img>` element tells assistive technology that the image is purely decorative and should be skipped — distinct from a missing `alt` attribute, which screen readers announce by reading the filename.
WCAG 2.1
WCAG 2.1 is the W3C accessibility standard published June 2018 that adds 17 success criteria to WCAG 2.0, focused on mobile, low-vision, and cognitive needs. It is the operative legal target referenced by the ADA and the EAA at Level AA.
WCAG 2.2
WCAG 2.2 is the W3C accessibility standard published October 2023 that adds 9 success criteria to WCAG 2.1, focused on focus visibility, target size, dragging alternatives, and accessible authentication.
Captions
Captions are time-synchronized text representations of the spoken dialogue, sound effects, and other audio in a video, used by deaf and hard-of-hearing viewers and by anyone watching with sound off.
Transcript
A transcript is the full textual record of an audio or video, including dialogue and significant non-speech audio. Transcripts make audio-only content accessible to deaf users and audio+video content accessible to deafblind users.
Heading hierarchy
Heading hierarchy is the nested structure of `<h1>`–`<h6>` elements on a page. A correct hierarchy starts at `<h1>` (one per page), nests `<h2>` sections inside, then `<h3>` subsections, without skipping levels.
Color blindness
Color blindness is a class of visual conditions in which the perception of certain colors is impaired or absent. The most common form, red-green color blindness, affects roughly 8% of men and 0.5% of women of Northern European descent.