What Is Web Accessibility (a11y)?
Web accessibility (a11y) is the practice of building websites and applications that people with disabilities can perceive, navigate, and interact with, including users relying on screen readers, keyboard-only navigation, or voice control. It is typically measured against the Web Content Accessibility Guidelines (WCAG), an international standard with three conformance levels: A, AA, and AAA. Most businesses aim for WCAG 2.1 or 2.2 level AA, which is also the legal baseline in many jurisdictions, including the EU.
Web accessibility, often abbreviated a11y, means designing and building websites that people with disabilities, including visual, motor, auditory, and cognitive impairments, can use effectively.
Accessibility is not a checkbox exercise for a niche audience. The World Health Organization estimates that around 16 percent of the global population lives with a significant disability, and that figure does not include temporary situations like a broken arm or a noisy environment that makes captions useful for anyone. A site built without accessibility in mind quietly excludes a meaningful share of potential customers and, increasingly, exposes the business to legal risk.
The four principles behind WCAG
The Web Content Accessibility Guidelines organize requirements around four principles, commonly abbreviated POUR. Content must be Perceivable, available through more than one sense, so images need alt text and videos need captions. It must be Operable, meaning every interactive element works with a keyboard alone, not just a mouse. It must be Understandable, with clear language, predictable navigation, and helpful error messages. And it must be Robust, meaning it works reliably across browsers and assistive technologies such as screen readers.
What this looks like in code
In practice, accessibility comes down to a set of concrete, testable details: semantic HTML elements used for their actual purpose rather than generic <div> soup, descriptive alt attributes on meaningful images, form labels properly associated with their inputs, a logical heading hierarchy with one <h1> per page, visible focus indicators for keyboard users, and sufficient contrast between text and background colors, typically a ratio of at least 4.5:1 for normal text under WCAG AA.
Why it matters for your business
Beyond the legal obligation under the European Accessibility Act, accessible sites tend to perform better on search engines, since much of the same structure, semantic HTML, descriptive alt text, clear headings, is what search crawlers and AI answer engines rely on to understand a page. Accessibility work and SEO work overlap more than most teams expect, so investing in one tends to improve the other.
How to check where you stand
Automated tools like axe DevTools, WAVE, or Lighthouse’s accessibility audit catch a meaningful share of common issues, roughly 30 to 40 percent of WCAG failures, in a few minutes. They cannot catch everything: contrast on background images, logical reading order, or whether alt text actually describes the image usefully all require a manual review, ideally including an actual test with a screen reader like NVDA or VoiceOver.
Getting started without a full audit
For a business without the budget for a full WCAG audit, the highest-value fixes are usually the cheapest: add alt text to every meaningful image, make sure every form field has a visible label, check color contrast on your primary buttons and body text, and confirm you can tab through the entire page and operate every interactive element without a mouse.
Our tip: Run your homepage and one key conversion page, like a contact form or checkout, through a free automated scanner such as WAVE. It takes minutes and typically surfaces the handful of fixes that matter most before you invest in a full accessibility audit.
Frequently asked questions
Why is 'a11y' used as shorthand for accessibility?
It is a numeronym: the letters a and y are kept, and the 11 letters in between (c-c-e-s-s-i-b-i-l-i-t) are replaced with the number 11. The same pattern produces i18n for internationalization and l10n for localization. It started as a shorthand in developer communities and is now used widely in accessibility documentation, tools, and job titles.
Is web accessibility a legal requirement?
In the EU, the European Accessibility Act requires many digital products and services, including ecommerce and banking, to meet accessibility standards from June 2025 onward, with WCAG 2.1 level AA as the common reference point. Public sector websites in EU member states have been under similar obligations since 2018 through the Web Accessibility Directive. Non-compliance can lead to complaints, fines, or legal action depending on the country and sector, so this is not purely a best-practice question anymore.
What are the most common accessibility mistakes on business websites?
The most frequent issues are images without alt text, form fields without associated labels, insufficient color contrast between text and background, interactive elements that cannot be reached or operated with a keyboard alone, and video content without captions. Most of these are inexpensive to fix once identified, which is why an accessibility audit early in a project saves far more time than fixing issues after launch.
Does accessibility work conflict with good design?
No, in most cases accessible design and good design are the same design. Clear color contrast, logical heading structure, readable font sizes, and predictable navigation benefit every visitor, not only people with disabilities. Accessibility becomes a conflict with design mainly when a visual concept relies on very low contrast or unconventional interaction patterns purely for aesthetic effect, which is a narrow case.