WCAG (Web Content Accessibility Guidelines).

WCAG is structured hierarchically. At the top are four principles: content must be perceivable, operable, understandable and robust. Below them are guidelines as general goals, and below those the success criteria: testable statements that are either met or not. Each success criterion is assigned a level: A as the minimum, AA as the practical benchmark, AAA as the maximum, which is rarely achievable in full for entire websites. The versions build on each other: WCAG 2.0 appeared in 2008, WCAG 2.1 in 2018, and WCAG 2.2 has been a W3C Recommendation since October 2023. A next generation is being drafted, but it is a draft and not applicable in practice.

Level AA requires things that can be measured. Text contrast of at least 4.5:1, and at least 3:1 for large text and for the outlines of controls. Full keyboard operability without keyboard traps, with a visible focus. Meaningful alt text, captions for videos, a correct heading hierarchy, form fields with permanently visible labels and error messages that name the affected field and give a hint on how to correct it. WCAG 2.2 added target sizes of at least 24 by 24 CSS pixels, an alternative to dragging movements, consistently placed help and authentication that does not force people to memorise things.

A concrete case from practice that comes up almost every time: the enquiry form with a button in the accent colour. A bright signal green on a white background looks strong but does not reach 4.5:1 against white; white text on it fails, dark text on it passes. The same check applies to placeholder text in fields, disabled buttons and grey hint text. The solution is not to abandon the brand, but a second, darker variant of the same colour for text and outlines. Once such values are stored as a design token, they are checked once rather than again for every new page.

Conformance is declared per page and per process, not across a whole website in one sweep. Automated tools such as Lighthouse or axe, experience shows, find only part of the violations, because understandability, a meaningful order and appropriate alt text cannot be judged by a machine; manual testing with a keyboard and a screen reader remains necessary. To be honest about the limits: so-called overlay tools, which promise accessibility after the fact via a script, do not replace conformance; disability organisations mostly view them critically. The legal situation in Switzerland and the EU is covered in the entry Digital Accessibility.