Web accessibility: a practical guide

The Web Content Accessibility Guidelines (WCAG) are the international standard for web accessibility, published by the W3C. The current version, WCAG 2.2, defines criteria organised into three conformance levels: A (minimum), AA (recommended for most sites) and AAA (maximum). Most legislation and contracts reference level AA as the baseline.

WCAG is built on four foundational principles: perceivable (content must be presentable through at least one sense), operable (the interface must work with various input devices), understandable (information and operation must be clear) and robust (content must work with current and future assistive technologies).

Accessibility spans every layer of development: semantic HTML, CSS styling and JavaScript behaviour. The starting point is using native HTML elements correctly — a <button> for actions, an <a> for navigation, hierarchical headings (<h1> through <h6>), and landmarks like <nav>, <main> and <aside>. This structure is automatically interpreted by screen readers without extra work.

Forms deserve particular attention: every field needs an associated <label>, errors must be announced accessibly (using aria-live or aria-describedby), and tab order must follow a logical sequence. Informative images require descriptive alt text; decorative ones take an empty alt attribute. Videos need captions and, ideally, audio descriptions.

Accessibility testing combines automated tools, manual review and real-user testing. No automated tool catches every issue — W3C estimates suggest they cover between 30% and 50% of WCAG criteria — but they are essential as a first line of defence.

axe DevTools (by Deque) is the industry reference for automated testing: it integrates as a browser extension, in CI/CD pipelines and with testing frameworks like Cypress or Playwright. Lighthouse includes accessibility audits in its overall score. WAVE, by WebAIM, provides an intuitive overlay of errors directly on the page. For manual testing, NVDA (Windows) and VoiceOver (macOS/iOS) are the most widely used screen readers.

Web accessibility is not just good practice — in many markets it is a legal obligation. The European Accessibility Act requires digital products and services to be accessible from June 2025 onwards, affecting ecommerce, digital banking, transport and telecommunications across the EU.

In the United States, the ADA (Americans with Disabilities Act) has been the basis for thousands of lawsuits against inaccessible websites. In the UK, the Equality Act 2010 applies similar obligations. Non-compliance can result in financial penalties, litigation and reputational damage that far outweighs the cost of doing it right.

Accessibility has a direct impact on business metrics. According to the WHO, over 1.3 billion people — 16% of the global population — live with some form of disability. Ignoring accessibility means excluding a massive segment of potential users and, by extension, customers.

Accessible sites tend to perform better in search rankings because search engines value semantic HTML, alt text and clear structure. They also show stronger conversion rates: accessible forms are easier for everyone to complete, clear navigation reduces bounce rates, and proper contrast improves readability in any context.

The annual WebAIM Million report analyses the top one million homepages and consistently finds the same problems. In 2025, 95.9% of homepages tested had automatically detectable WCAG failures. The most frequent errors are surprisingly basic and straightforward to fix.

Insufficient text contrast is the most prevalent issue (81% of pages), followed by images without alt text, empty links, form fields without labels, and buttons without accessible names. These five errors account for the vast majority of detected barriers. Fixing them requires no advanced expertise — just development discipline.