Accessibility (A11y)

Accessibility means designing websites and tools so people with disabilities can use them. Planning it from the beginning can reduce the need to redo work later. Try using one web page with only your keyboard and note any controls you cannot use.

Web accessibility means people with disabilities can perceive, understand, navigate, interact with and contribute to the Web. Accessibility planning belongs at the beginning of a project, with evaluation early and throughout development. W3C's guidance recommends this approach to reduce rework and identify problems while they are easier to address [1].

The Web Content Accessibility Guidelines (WCAG) describe accessibility requirements. Four principles help organize them: Perceivable means information is available through ways users can perceive; Operable means users can navigate and interact; Understandable means content and controls make sense; Robust means content can be reliably interpreted by browsers and assistive technologies—tools that help people with disabilities use digital content [2].

In a hypothetical website, a search button displays a magnifying glass. Its text alternative—text conveying the image's purpose—could be “Search,” rather than merely “magnifying glass.” A screen reader, software that reads page information aloud, can convey that purpose. This depends on the website providing the information and the browser and assistive technology processing it correctly [1][2].

Keyboard access is one part of Operable design. Check whether you can reach and activate controls without a mouse or becoming trapped. Keyboard focus—the current location of keyboard interaction—should be visible and follow a meaningful order. Under Understandable design, descriptive instructions and error messages help people avoid and correct mistakes [2].

Accessibility can also help people with temporary disabilities, changing abilities with age or situational limitations, such as being unable to listen to audio. These are benefits described in official guidance, rather than measured effects from an experiment. A keyboard check examines only part of accessibility: no evaluation tool alone can determine whether a site meets accessibility guidelines, and knowledgeable human evaluation is required [1].

• Planning guidance: WAI recommends incorporating accessibility from the beginning of projects and evaluating it early and throughout development. This is practical guidance, not an experiment establishing a fixed saving in time or money [1]
• Text-alternative guidance: Alternatives should convey an image's purpose or function. WAI illustrates this with “search” for a search button, rather than a description of its magnifying-glass appearance; browsers and assistive technologies must also process that information [2]
• Conditional guidance: WAI's overview includes mechanisms to stop, extend or adjust time limits, except where necessary, and to switch off animations unless they are essential. These qualifications should remain attached to the advice [2]
• Evaluation guidance: Tools can help assess accessibility, but no tool alone can determine whether a site meets accessibility guidelines. WAI calls for knowledgeable human evaluation [1]

These sources are official guidance documents, not experiments establishing universal benefits or numerical effects. Accessibility Principles explicitly provides an incomplete overview of requirements; its examples should not be treated as a complete WCAG assessment or a legal compliance guarantee. A keyboard check covers only part of accessibility, and accessibility depends on content, browsers, authoring tools and assistive technologies working together [1][2]. Citation correction: the earlier lesson's attribution of the four principles to “Introduction to Web Accessibility (2024)” is replaced here with Accessibility Principles [2]. The old year is not treated as verified; both supplied bibliography years remain null.