Accessibility needs a yardstick, and almost everywhere that yardstick is the WCAG. Laws and standards such as Switzerland’s eCH-0059, the European standard EN 301 549 and the European Accessibility Act refer to it rather than inventing their own criteria.
Principles and levels
The WCAG assign their success criteria to four principles. Perceivable: content must be accessible without sight or hearing, for example through text alternatives and captions. Operable: everything must work by keyboard, with enough time and without seizure triggers. Understandable: language, navigation and forms must be predictable. Robust: the code must work with assistive technologies such as screen readers. Each criterion has a level; in practice AA is the usual target, because AAA cannot be met for all content.
WCAG 2.1 and 2.2
WCAG 2.2 has been a W3C Recommendation since October 2023 and adds criteria to 2.1, for example on keyboard focus visibility, target size, alternatives to dragging and accessible authentication. Switzerland’s eCH-0059 version 3.0 requires WCAG 2.1 level AA for the federal administration. Anyone building today should aim for 2.2, which is backwards compatible.
The most common failures
Insufficient colour contrast, images without text alternatives, form fields without associated labels, elements that only work with a mouse, no visible focus, vague link texts like “here” and a heading structure that exists only visually. Many of these also affect search engine optimisation, because clean structure and text alternatives help machines too.
Testing
Automated tools find part of the problems, such as contrast and missing attributes. Whether a text alternative makes sense, whether the reading order is right or whether a dialog works with a screen reader only a manual test can show. A reliable audit combines both and documents deviations in an accessibility statement. The steps are in our accessibility checklist.