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The four principles of WCAG

Want to create a website, app or digital document that really works for everyone? Then it's important to understand the four principles of WCAG. These principles form the basis of digital accessibility. In this article, we explain them clearly, with examples and tips for practice.

What is WCAG?

WCAG stands for Web Content Accessibility Guidelines. These are international guidelines that explain how to make digital information accessible to people with disabilities. WCAG was created by the World Wide Web Consortium (W3C).

The current version that most legislation relies on is WCAG 2.1 level AA. Soon WCAG 2.2 will become important, and WCAG 3.0 is under development.

WCAG is made up of four principles. These principles help you make digital content understandable, usable and accessible to all.

The four principles of WCAG

The four principles of WCAG together form the word POUR (English for ‘casting’). This stands for:

  1. Perceivable
  2. Operable
  3. Understandable
  4. Robust - robust

Below we explain each principle in plain language.

1. Perceivable.

Every user should be able to perceive the information on your Web site. That means offering information in different ways so that everyone can see, hear or read it.

Examples:

  • Add alternative text to images so that blind users can understand what is in the image via a screen reader.
  • Make sure videos have subtitles or a transcript so that hearing-impaired or deaf users can also follow the content.
  • Use sufficient color contrast between text and background so that people with visual impairments can read the text clearly.
  • Use headings and lists in a clear way so that screen readers can read the structure properly.

Tip: Ask yourself the question, “Can someone who cannot see or hear still understand this content?”

2. Operable.

All functions on your website should be operable by different people, even if they cannot use a mouse.

Examples:

  • Make sure your website works properly using only a keyboard (such as via Tab and Enter).
  • Give interactive components such as buttons and links sufficient focus and visible indication.
  • Use clear labels for forms so someone knows what to fill out.
  • Avoid flickering content that can cause seizures.

Tip: Test your website without a mouse. Can you still use everything? If so, chances are you're well on your way.

3. Understandable.

The content as well as the operation of your website should be understandable. Not only for people with disabilities, but for everyone.

Examples:

  • Use clear and simple language (such as language level B1) so that more people understand your texts.
  • Make sure forms are logically structured, with explanations for each field.
  • Use consistent navigation and formatting so that users quickly learn how the site works.
  • Provide error messages on forms that really help people solve the problem.

Tip: Let another person use your website without explanation. Does that person understand what is happening? If so, you're on the right track.

4. Robust (Robust).

Your website must work well with different devices, browsers and assistive technologies, now and in the future. That's what we call robust.

Examples:

  • Use correct HTML code so that screen readers can properly interpret the content.
  • Test your website in multiple browsers and on different screen sizes.
  • Make sure content is not dependent on JavaScript alone or specific plugins.
  • Use modern web standards so that your content remains accessible even with updates.

Tip: Have your website tested with a screen reader or accessibility tool to see if everything works as it should.

Why are these principles important?

The four principles of WCAG are not strict rules, but are a framework for thinking. They help you think about how different people use your content - with their eyes, ears, hands or assistive technology.

By applying these principles:

  • make your Web site accessible to people with disabilities,
  • improve usability for everyone (including the elderly, those with little digital experience, or those with stress),
  • Meet the requirements of laws such as the Digital Government Act and the European Accessibility Act.

So accessibility is not an extra, but an essential part of good design.

How do you begin?

Want to improve your website or app based on the four WCAG principles? Then start with these steps:

  1. Read the WCAG in plain language - B1-level summaries and checklists are available.
  2. Perform an accessibility scan - For example, with WAVE or Axe.
  3. Add structural improvements - Think alt text, keyboard navigation and clear language.
  4. Engage users - Ask people with different disabilities for feedback.
  5. Have a manual accessibility audit done - This will give you targeted advice and insight into what could be improved.

Summary

The WCAG helps you make digital content accessible. The four principles are:

  • Observable: the information must be visible or audible to all.
  • Operable: the website should be usable with mouse, keyboard or other tools.
  • Understandable: everything must be clear and logical, in language and operation.
  • Robust: the website should work well with different browsers and assistive technologies.

If you work with these principles, then you are taking a big step toward an inclusive digital world.

Want to learn more about digital accessibility?

Find more articles on WCAG, legislation and practical tips in our knowledge base:

  • What is WCAG?
  • How do you apply digital accessibility?
  • What is the European Accessibility Act?

Or contact us for advice or a customized accessibility audit.