WCAG
WCAG (Web Content Accessibility Guidelines) are the W3C recommendations that define how to make a website usable by everyone, including people with disabilities. Most legislation worldwide, including RGAA in France, relies on WCAG level AA as a compliance requirement.
95.9% of the home pages of the most visited websites in the world have at least one detectable accessibility error. That's the finding from WebAIM Million 2024. And automated tools only detect about 40% of real problems.
WCAG is the reference standard that defines what we mean by "accessibility error."
#Four principles, one acronym
The WCAG are organized around four principles, summed up by the English acronym POUR:
- Perceivable: content must be perceivable by each user. An image has alternative text. A video has captions.
- Operable: the interface works with a keyboard, not just a mouse. Animations can be paused.
- Understandable: the interface's behavior is predictable. Error messages in forms are explicit.
- Robust: the code is clean enough to be interpreted by assistive technologies such as screen readers.
Each principle is broken down into testable success criteria.
#Levels A, AA, AAA: which one to aim for?
WCAG defines three levels of conformance. Level A covers the bare minimum: without it, certain content is inaccessible. Level AA is the target of virtually all legislation, including RGAA in France and the European standard EN 301 549.
Level AAA imposes requirements such as a contrast ratio of 7:1 or simplified reading levels. The W3C itself recommends against requiring it for an entire website. Aim for it on critical sections, not as a global objective.
#The automation trap
56.8 errors per page on average, still according to WebAIM. These figures only reflect what a scanner can detect. A tool checks whether an alt attribute exists on an image. It doesn't check whether that text correctly describes the image.
WCAG conformance cannot be verified with a scanner alone.
#Summary
WCAG is the technical foundation of web accessibility. The current version is WCAG 2.2, published in October 2023. For a website subject to a legal obligation, aim for level AA. And keep in mind that accessibility is also tested manually, with real users and assistive technologies.