1 Understanding web accessibility

Web accessibility is presented as a practical way of making digital products usable by as many people as possible, not only for people with disabilities but for anyone whose abilities or circumstances change over time. The chapter emphasizes that accessibility should be invisible when done well: content should be perceivable, interfaces operable, information understandable, and systems robust enough to work across devices, assistive technologies, and varied user contexts. In that sense, accessibility is not a special feature added at the end, but a core part of building technology that works for real humans.

The chapter also argues that accessibility belongs in every phase of a web project, from requirements and design through development, testing, deployment, content management, and support. Ignoring it creates technical debt, because inaccessible patterns become embedded in code, workflows, and organizational habits, making later fixes more costly. Accessibility influences usability, supports maintainable code, improves the experience for all users, and helps teams align product decisions with legal, ethical, commercial, and technical responsibilities.

A major part of the chapter explains the role of WCAG as the main technical foundation for accessibility law and practice worldwide. WCAG is organized around the four POUR principles and uses testable success criteria at levels A, AA, and AAA, supported by techniques, understanding documents, and testing guidance. The chapter closes by stressing that conformance is ongoing rather than a one-time achievement: as content and technology change, accessibility must be maintained continuously, with WCAG 2.2 currently the practical reference point and WCAG 3 pointing toward a more flexible future.

Accessibility impacts nearly all aspects of software development, from planning and design to post-launch content management and support. Everyone has a responsibility to ensure users can actually access content and functionality.

This image illustrates the various components in WCAG 2.2. Guidelines are organized under four principles. For each of the 13 guidelines, there are several normative success criteria that can be categorized at levels A, AA, or AAA. For each success criterion, WCAG also provides supporting informative documentation, including techniques, understanding documents, testing rules, and additional guidance.

The four principles underpinning WCAG 2.2 – and the associated guidelines and success criteria – ensure that technology is accessible to the widest range of people, regardless of differences in ability, whether permanent, temporary, or situational. Content and functionality must be perceivable through different senses, operable in different ways, understandable and predictable, and robust across a wide range of technologies, including assistive technologies.

Distribution of WCAG 2.2 success criteria across conformance levels (A, AA, AAA). This highlights the relative size and complexity of higher conformance levels.

The stages of building accessible web applications: understanding accessibility standards and regulations, determining core web technologies for accessible content and functionality, designing inclusive security, addressing modern web-app challenges, and sustaining accessibility over time.

• Accessibility is not just for people with disabilities – it improves usability and experience for everyone.
• Accessibility is not another step in your QA processes; it reflects core engineering competence and responsible product development and management. It belongs at the heart of your process, not at the end.
• Accessibility matters for societal, commercial, legal, and technical reasons – it’s the right thing to do, and doing it well means you’re building things the right way.
• In many jurisdictions around the world, accessibility is not optional – it is a legal requirement.
• Most accessibility laws worldwide reference or align with the W3C’s Accessibility Guidelines (WCAG), the globally recognized standard for digital accessibility. WCAG is created through a rigorous, collaborative process involving hundreds of contributors from industry, government, academia, and accessibility communities, with the goal of providing a single, widely accepted set of guidelines.
• WCAG 2.2 is organized around 4 principles, which are broken down into 13 guidelines. Each guideline includes a set of testable success criteria (normative), defined at three conformance levels: A, AA, and AAA. WCAG also provides additional informative documentation to help interpret and meet the success criteria, including sufficient and advisory techniques, as well as common failures.
• Accessibility conformance is not a one-and-done activity – but an ongoing process. Embedding it into your workflow helps ensure quality, reduce risk, and keep your product future-proof.

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