WCAG 2.1 AA: what it actually asks of your website

The Web Content Accessibility Guidelines (WCAG) 2.1, Level AA, are the technical baseline referenced by the European Accessibility Act via EN 301 549 — and by the ADA case law in the US. Here is what they mean in practice.

The four principles (POUR)

• Perceivable — content must be presentable in ways users can perceive: text alternatives for images, captions for video, sufficient colour contrast (4.5:1 for normal text), content that reflows on small screens.
• Operable — everything must work with a keyboard alone; users need visible focus, enough time, no seizure-inducing flashes, and clear navigation (page titles, link purpose, headings).
• Understandable — declare the page language, keep navigation consistent, label form fields and describe errors in text.
• Robust — valid, semantic markup that assistive technologies (screen readers) can interpret; correct name/role/value on custom controls.

The violations we see most often

• Insufficient colour contrast (the single most common failure — and fully machine-fixable).
• Images without alt attributes.
• Form inputs without programmatic labels.
• Links and buttons without discernible text (icon-only controls).
• Missing document language and landmark structure.

What automation can and cannot test

Automated engines like axe-core reliably detect roughly 30–57% of accessibility issues by volume (contrast, missing attributes, structural problems) with near-zero false positives. They cannot judge whether alt text is meaningful, whether focus order makes sense, or whether captions are accurate — those need human review. A serious compliance process combines both; a clean automated scan is the necessary starting point, not the finish line.

Reference: WCAG 2.1 specification (W3C). This guide is general information, not legal advice.