WCAG

WCAG is a set of rules for how websites and apps should be built. The goal is that people with a disability can use them without outside help. This includes, for example, blind people, people with visual impairments, or those who cannot operate a mouse. The abbreviation stands for Web Content Accessibility Guidelines. It is published by the W3C, an international organization that sets the technical standards of the internet. The rules are not just one recommendation among many: in the EU and many other countries, laws require public authorities and an increasing number of companies to comply with them.

When a website locks people out

Around one in ten people in Germany lives with a recognized disability. Those who cannot see have websites read aloud to them by a program. This program is called a screen reader and reads the page’s code aloud. If a photo has no text description, the screen reader just says “graphic.” An order button without a label thus becomes unusable.

This affects far more people than just the narrow target group. Subtitles in videos also help on a noisy bus. Good contrast helps everyone in sunlight on a display. A page that can be operated entirely by keyboard is even faster for experienced users. Experts call this the curb-cut effect: the lowered curb was built for wheelchairs, but is used by strollers, suitcases, and bicycles.

On top of that comes legal pressure. Since June 2025, the Accessibility Strengthening Act (Barrierefreiheitsstärkungsgesetz) has been in force in Germany. It also obligates private providers, such as online shops and banking apps, to ensure accessibility. WCAG serves as the benchmark here. Those who ignore it risk warnings and fines.

Four principles and three levels

WCAG assigns all requirements to four basic principles. Content must be perceivable, meaning accessible through more than one sense. It must be operable, for example even without a mouse. It must be understandable, meaning clearly labeled and predictable. And it must be robust, so that assistive technologies can also interpret it correctly.

Under these principles are around eighty individual success criteria. Each one is a verifiable statement, not a vague wish. One example: text must stand out from the background with a ratio of at least 4.5 to 1. Another: every image needs alternative text that describes its content. A third: videos need subtitles.

The criteria are sorted into three levels: A, AA, and AAA. Level A is the absolute minimum, without which a page remains completely unusable for some people. Level AA is considered the practical standard and is what laws usually require. Level AAA is the strictest tier and is often unrealistic for entire websites. A common misconception is that accessibility is a matter of design. In fact, it is mainly the clean structure of the code behind the scenes that decides.

From school platforms to testing tools

You encounter WCAG every day without noticing. The descriptive text under an image on social networks goes back to it. So do automatic subtitles on videos or dark mode with sufficient contrast. Digital school platforms and government portals must also meet the requirements.

In practice, developers test their pages with tools like Lighthouse, which is built into the Chrome browser. However, such programs only find part of the problems, roughly estimated at a third. Whether an alt text meaningfully describes an image can so far only be judged by a human. This is exactly where AI tools are now stepping in, automatically suggesting image descriptions.

In business news, the term usually appears in connection with lawsuits or deadlines. Large corporations have already been sued because their online shops were unusable for blind customers. WCAG should be distinguished from the EN 301 549 standard, the European standard. This standard largely adopts the WCAG criteria and supplements them with requirements for hardware and software.