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WCAG & A11y Fundamentals

The Web Content Accessibility Guidelines (WCAG) are the globally recognized framework for digital accessibility. Published by the World Wide Web Consortium (W3C), they describe specific requirements for websites, apps, and other digital content to make them accessible to as many people as possible.

The POUR Principle

The WCAG are based on four overarching principles that serve as the foundation for any accessible digital application:

  • Perceivable: Content must be designed so that it can be perceived by all user groups with their respective sensory perceptions (e.g., alternative texts for images, sufficient color contrast, subtitles for videos).
  • Operable: All functions must be usable without a mouse – for example, via keyboard or voice control. Focus guidance, controls, and interactions must be intuitive and accessible.
  • Understandable: Content and operation should be clearly structured and predictable – with understandable language, consistent navigation, and clear feedback for actions.
  • Robust: Content must work with a variety of browsers, devices, and assistive technologies – through semantically correct HTML and clean implementation of ARIA roles.

Structure and Functionality of WCAG

The WCAG are organized into guidelines and success criteria:

  • Each of the four principles contains several guidelines (13 in total) that describe general goals.
  • These guidelines are operationalized through specific success criteria – in the current version WCAG 2.2, there are over 80 in total.
  • Each success criterion is assigned to one of three conformance levels:
    • Level A: Minimum requirements for basic accessibility (e.g., no keyboard traps, alternative texts for images).
    • Level AA: Recommended standard in many laws – significantly improves usability (e.g., sufficient color contrasts, visible keyboard focus).
    • Level AAA: Very high requirements – for specialized applications or content with particularly high accessibility demands (e.g., captioning of live events, very simple language).

Important: The conformance levels build upon each other. Level AA includes all criteria from Level A and adds additional requirements. Level AAA in turn includes all requirements from Level A and AA – and provides additional specifications for particularly comprehensive accessibility.

The conformity of a website is assessed based on these criteria. In practice, Level AA is the recognized target standard.

WCAG 2.2 – Current Status

Since October 2023, WCAG 2.2 has been officially published. This version supplements WCAG 2.1 with new success criteria – particularly to support:

  • Users with cognitive limitations (e.g., clearly identifiable target sizes)
  • User-friendliness on touchscreens and mobile devices

Organizations should implement WCAG 2.2 where possible, even if legal requirements such as BITV currently still prescribe WCAG 2.1 as the minimum standard.

Significance for Everyday Use

The WCAG serve as an evaluation standard for accessibility – in development, design, and testing. They are used worldwide in training, certifications, and product evaluation. Additionally, they form the substantive basis for legal requirements for digital accessibility in many laws (e.g., BFSG, EAA, BITV).

The consistent application of WCAG helps make digital products accessible, usable, and understandable for all people – regardless of abilities, devices, or personal circumstances.