Web accessibility glossary

Short, plain-language definitions of the terms you meet in accessibility reports, laws and standards. Links lead to our longer guides where they exist.

Laws and standards

ADA (Americans with Disabilities Act) — US civil rights law. Title III covers businesses open to the public and is the basis of most US website lawsuits; Title II covers state and local governments. See ADA website compliance.

Annex V — the part of the European Accessibility Act that lists what the information on accessibility for services must contain. See the statement guide.

BFSG (Barrierefreiheitsstärkungsgesetz) — the German law implementing the EAA. See BFSG guide.

Conformance level (A, AA, AAA) — WCAG success criteria are grouped in three levels. Laws and standards usually reference level AA, which includes all A criteria.

EAA (European Accessibility Act) — Directive (EU) 2019/882. Requires certain products and consumer services, including e-commerce, to be accessible; applies to services since 28 June 2025. See EAA guide.

EN 301 549 — the European standard for accessibility of ICT products and services. Its web chapter follows WCAG. V3.2.1 is based on WCAG 2.1; V4.1.1, published in September 2026, is based on WCAG 2.2.

Harmonised standard — a European standard cited in the Official Journal of the EU. Meeting it gives a presumption of conformity with the legal requirements it covers.

Micro-enterprise — under the EAA, a business with fewer than 10 employees and turnover or balance sheet total of no more than €2 million. Exempt from the service requirements. See who the EAA applies to.

Section 508 — US rule for federal agencies' ICT; references WCAG 2.0 AA.

VPAT / ACR — Voluntary Product Accessibility Template and the Accessibility Conformance Report produced with it; common in US procurement.

WCAG (Web Content Accessibility Guidelines) — the W3C guidelines for accessible web content. Current version: 2.2. Organised under four principles: perceivable, operable, understandable, robust.

Success criterion (SC) — a single testable WCAG requirement, such as 1.4.3 Contrast (Minimum).

Testing and tools

Automated testing — software that checks pages against rules. Fast and repeatable, but finds only part of the issues.

axe-core — an open-source accessibility testing engine by Deque. Used by many tools, including ours.

Manual testing — a person checks keyboard use, focus, meaning of alt text, error messages and screen reader behaviour.

Monitoring — repeating automated checks on a schedule to catch new issues after site changes.

Overlay — a script that adds an accessibility toolbar or automatic "repairs" on top of a site. Does not fix the underlying code. See why overlays are not a solution.

Concepts on the page

Accessible name — the name assistive technology announces for a button, link or field, e.g. "Add to cart".

Alt text (text alternative) — a short description of an image for people who cannot see it. Decorative images get empty alt text.

ARIA — WAI-ARIA attributes that add roles, states and names for assistive technology. Useful when used correctly; wrong ARIA can make things worse.

Assistive technology — software or hardware people use to access computers: screen readers, magnifiers, voice control, switch devices.

Contrast ratio — the difference in luminance between text and background, from 1:1 to 21:1. WCAG AA asks for at least 4.5:1 for normal text.

Focus indicator — the visible outline that shows which element is selected when using a keyboard.

Keyboard trap — a place where keyboard focus gets stuck, often in pop-ups or chat widgets.

Label — visible text connected to a form field, telling the user what to enter.

Screen reader — software that reads the screen aloud or in braille, such as NVDA, JAWS or VoiceOver.

Target size — the clickable area of a control. WCAG 2.2 asks for at least 24 × 24 CSS pixels or enough spacing (SC 2.5.8).

Our service

Our reports use these terms with a short explanation for business owners. They are an automated check, not a full audit, and not legal advice. Try a free check or read the WCAG 2.2 checklist.