Accessibility Baseline

An accessibility baseline, as used in WCAG 2.0 and later versions, is the set of technologies that a content author assumes are supported and enabled in the user agents (browsers and assistive technologies) used by their target audience. Authors must ensure that all content conforms to WCAG even when a user agent supports only the technologies in the baseline. The baseline concept acknowledges that web accessibility is a shared responsibility between content and user agents — if a technology like JavaScript is in the baseline, authors can rely on it for accessibility features, but if it is not, they must provide alternatives. Baselines may be set by governments, organizations, or clients, and they vary by context. For example, an intranet where all users have modern browsers has a different baseline than a public website that must support older assistive technologies.