Accessibility glossary

The terms you'll meet in the portal, in plain English.

WCAG — Web Content Accessibility Guidelines. The international standard for accessible web content, published by the W3C. Version 2.2 is current. Almost every accessibility law in the world points at WCAG for its technical requirements.

Conformance levels: A, AA, AAA — three tiers of strictness. AA is the practical target and the level referenced by most laws and by Zylyn's scans. AAA is aspirational and rarely required wholesale.

Success criterion — a single numbered requirement within WCAG, like 1.4.3 Contrast (Minimum). When a finding is tagged WCAG AA · 1.4.3, that's the specific rule being failed.

POUR — the four WCAG principles: content must be Perceivable, Operable, Understandable and Robust.

Best practice — in Zylyn, a finding tagged WCAG BEST PRACTICE is a recommendation that improves accessibility but is not a WCAG failure. Worth fixing; doesn't count against conformance.

ADA — Americans with Disabilities Act (US, 1990). Civil rights law applied to websites through litigation rather than a fixed technical deadline. Courts generally treat WCAG AA as the benchmark.

Section 508 — US federal law requiring accessible technology in federal agencies and their suppliers. Drives the VPAT requirement in government procurement.

EAA — European Accessibility Act. Enforceable since 28 June 2025 for products and services placed on the EU market.

EN 301 549 — the European technical standard behind the EAA. Its digital core is WCAG.

AODA — Accessibility for Ontarians with Disabilities Act (Ontario, Canada).

Unruh Act — California civil rights law often used alongside the ADA in web accessibility claims.

VPAT / ACR — a Voluntary Product Accessibility Template is the blank form; a completed one is an Accessibility Conformance Report. Government and enterprise buyers often require one before evaluating a product. Not currently self-serve in Zylyn.

PDF/UA — the accessibility standard for PDF documents. See checking PDFs.

Screen reader — software that reads page content aloud for blind and low-vision users. The common ones are NVDA and JAWS on Windows and VoiceOver on Apple devices.

Assistive technology (AT) — the umbrella term: screen readers, magnifiers, switch devices, voice control, braille displays.

Alt text — the text alternative on an image, read aloud in place of the picture. Decorative images should have empty alt text so screen readers skip them; informative images need a real description.

Contrast ratio — the measured difference between text and background colour. WCAG AA requires 4.5:1 for normal text and 3:1 for large text. Zylyn reports the measured ratio and both colour values.

Landmark — a structural region of a page (main, nav, header, footer) that lets screen reader users jump straight to the part they want.

Skip link — a link at the very top of a page, often visible only on keyboard focus, that jumps past the navigation to the main content.

Focus order — the sequence in which elements receive focus as you press Tab. It should follow the visual reading order.

Focus indicator — the visible outline showing which element is focused. Removing it (a common CSS "tidy-up") makes a site unusable by keyboard.

ARIA — Accessible Rich Internet Applications: extra HTML attributes that describe custom components to assistive technology. Powerful and easy to get wrong — incorrect ARIA is worse than none.

Accessible name — the label assistive technology announces for a control. A button containing only an icon has no accessible name unless you add one.