What is WCAG? The guidelines for an accessible website
3 min read below · WebYes knowledge base
WCAG explained: the four principles, levels A, AA and AAA, the difference between 2.1 and 2.2 and how to test your website against the guidelines.
WCAG (Web Content Accessibility Guidelines) is the international standard for accessible websites and apps, published by the W3C. The guidelines are built around four principles and three levels; level AA is the norm that Dutch and EU legislation refers to.
The four principles of WCAG
All WCAG criteria fall under four principles. Perceivable: information must be visible or audible to everyone, for instance through alt texts on images and captions on video. Operable: every function must also work without a mouse, using a keyboard or voice control. Understandable: copy, navigation and error messages must be clear. Robust: the site must work well with different browsers and assistive technology, such as screen readers.
Each principle is broken down into concrete success criteria. Think of a minimum contrast ratio of 4.5:1 for normal text, a visible focus indicator during keyboard navigation and form fields with an associated label.
Levels A, AA and AAA
WCAG has three levels. Level A covers the absolute basics; without those criteria a site is unusable for some groups. Level AA is the legal norm for governments and, through the European Accessibility Act, for many commercial services. Level AAA is the strictest level and rarely fully achievable for an entire site.
| Level | What it means | When it matters |
|---|---|---|
| A | Minimal accessibility, removes the worst barriers | Always, for every website |
| AA | The practical norm: contrast, navigation, forms | Legal requirement for government and many businesses |
| AAA | Strictest requirements, such as sign language for video | Specific audiences or components |
WCAG 2.1 or 2.2: which version should you use?
WCAG 2.2 is the current version of the guidelines and adds a limited number of criteria to 2.1, including visible focus, drag movements and the size of click targets. Anything that meets 2.2 also meets 2.1. In Europe, legislation refers to WCAG through the EN 301 549 standard; the Dutch regulator ACM advises businesses to work with WCAG 2.2 straight away.
For new builds there is no reason to keep testing against 2.1. The WebYes scan therefore uses WCAG 2.2 AA as the basis for the accessibility pillar.
How to test your website against WCAG
Automated tools find the measurable problems: missing alt texts, contrast errors, empty buttons, missing labels and errors in the HTML structure. That is the fastest way to surface the biggest issues. A full WCAG audit also requires manual research, because criteria such as understandable error messages and a logical reading order cannot be judged by a machine.
A practical approach: run an automated scan first, fix the findings, and then walk through the key tasks on your site (ordering, contacting, logging in) manually with a keyboard and a screen reader.
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Frequently asked questions
Is WCAG legally required?
WCAG itself is a technical standard, not a law. But Dutch and European legislation refers to it: governments must meet WCAG level AA, and through the European Accessibility Act the same applies to many web shops and online services. In practice, WCAG AA is the legal yardstick.
How many WCAG criteria can an automated scan test?
Roughly 30 to 50 percent of the success criteria can be checked automatically. The rest requires human judgement, such as whether alt texts are meaningful or whether a form is logically structured. A scan is the starting point, not the finish line.
What is the difference between WCAG and EN 301 549?
EN 301 549 is the European standard for ICT accessibility and covers apps, documents and hardware in addition to websites. For web content, EN 301 549 refers directly to the WCAG criteria. If you meet WCAG AA, your website meets the relevant part of EN 301 549.
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