Web accessibility definition
Web accessibility means building websites that people with disabilities can perceive and operate, whether they listen to the page through a screen reader or navigate it by keyboard alone. It is measured against the WCAG guidelines, usually at level AA.
Web accessibility is about whether a site still works for people who don't use it the way its designer does. Blind users listen to it through a screen reader. Someone with a tremor or RSI tabs through it with a keyboard. People with low vision zoom in until a three-column layout has to collapse into one, and people with cognitive disabilities depend on plain structure and things behaving the same way twice.
The reference standard is the Web Content Accessibility Guidelines (WCAG), published by the W3C. Every success criterion has a level, A, AA or AAA, and European law and public procurement point to AA through the harmonised standard EN 301 549.
What does WCAG AA actually ask for?
Most of it is ordinary front-end discipline. The criteria that trip up marketing sites tend to be these:
- Text contrast of at least 4.5:1 against the background, or 3:1 for large text. Light grey body copy on white rarely makes it.
- Everything clickable works from the keyboard, with a visible focus outline. Custom dropdowns and cookie banners are the usual offenders.
- Images that carry meaning have alt text.
- Form fields have labels, and an error is explained in words as well as in red.
- Anything that moves by itself for more than five seconds, such as a carousel, can be paused.
Is web accessibility a legal requirement?
In the EU it is for a growing number of organisations. The Web Accessibility Directive has applied to public sector websites since 2019, and since 28 June 2025 the European Accessibility Act has covered a set of consumer services, e-commerce among them. A company that sells only to other businesses usually falls outside both, though a public-sector customer can still write accessibility into the contract.
How do you test a site for accessibility?
Automated checkers such as axe or Lighthouse catch the mechanical problems, like missing form labels and low contrast. They can't tell whether an alt text makes sense or whether the reading order matches what you see. For that, put the mouse away and tab through the page, then listen to it with VoiceOver or NVDA. Ten minutes of that on the homepage and the contact form will tell you more than a 100 score in Lighthouse.
Related terms
- Alt textAlt text is a short written description of an image, stored in the alt attribute of an HTML img element. Screen readers read it aloud and browsers show it when the image fails to load. Good alt text says what the image means in that spot on the page.
- Web Accessibility DirectiveThe Web Accessibility Directive, (EU) 2016/2102, is the EU law that requires public sector websites and mobile apps to be accessible. In practice that means meeting WCAG 2.1 level AA through the standard EN 301 549 and publishing an accessibility statement.
- TooltipA tooltip is a small text label that appears when you hover over or keyboard-focus an element, such as an icon button, to say what it is or does. It disappears when the pointer or focus moves away. Tooltips hold short, optional text and shouldn't contain links or buttons.
- TypographyTypography is the craft of choosing and arranging type so text is easy to read and its hierarchy is obvious. It covers typeface, size, line height, line length and spacing. On a website it also covers how fonts load and how text scales between screen sizes.