# Web accessibility

Category: [Technical SEO](https://seo-geo-glossary.com/en/glossary/category/technical-seo/) › [HTML, mobile & accessibility](https://seo-geo-glossary.com/en/glossary/category/technical-seo/html-mobile-accessibility/) · Also known as: accessibility, a11y, digital accessibility

**Web accessibility** means that websites, tools and technologies are designed so that people with disabilities can use them. W3C names auditory, cognitive, neurological, physical, speech and visual disabilities. In practice this covers sites that work with a screen reader, a keyboard or voice control.

## Who benefits?

W3C notes that accessible design also helps older adults, people on small screens or slow connections, and anyone with a temporary limitation such as a broken arm or bright sunlight on the screen.

## What is the technical standard?

The reference for web content is the Web Content Accessibility Guidelines (WCAG) from W3C. They are organized around four principles: perceivable, operable, understandable and robust. WCAG 2.2 is also published as ISO/IEC 40500:2025.

## Which rules apply?

In the US, the Department of Justice's 2024 rule under Title II of the ADA sets WCAG 2.1 Level AA as the technical standard for web content and mobile apps of state and local governments. ADA.gov lists compliance dates in 2027 and 2028 after an extension and publishes separate guidance on web accessibility under the ADA. In the EU, Directive (EU) 2019/882, the European Accessibility Act, covers accessibility requirements for certain products and services. Germany implements it in the Barrierefreiheitsstärkungsgesetz (BFSG), which covers services provided after June 28, 2025, including e-commerce services.

This is not legal advice.

## Accessibility and SEO

W3C points out that alt text for images, transcripts and keyboard navigation make content easier for search engines and other automated systems to use. Both areas rely on clean markup, descriptive link text and a logical heading structure (assessment). Google has not named accessibility as a ranking factor.

## Example

```html
<img src="/img/revenue-2026.png" alt="Line chart: revenue rises from January to June">
```

The alt text describes what the image shows, so a screen reader can convey it.

## Common mistakes

- **Missing alt attribute.** Without the attribute, some screen readers announce the image's file name, according to W3C.
- **Descriptive text on decorative images.** For purely decorative images W3C provides an empty `alt=""` so assistive technology skips them. Text would only add clutter to the output.
- **Too little contrast.** WCAG 1.4.3 (level AA) requires a contrast ratio of at least 4.5:1 for text and 3:1 for large text.
- **Link text without meaning.** Google advises against generic phrases such as "click here". Link text should describe where the link leads.

## FAQ

**What are the four principles?**
Perceivable, operable, understandable, robust (POUR).

**Is WCAG legally required?**
WCAG is a standard. It becomes binding where a law or regulation refers to it.

## Related terms

- [WCAG](https://seo-geo-glossary.com/en/glossary/wcag/index.md)
- [Alt text](https://seo-geo-glossary.com/en/glossary/alt-text/index.md)
- [Accessibility tree](https://seo-geo-glossary.com/en/glossary/accessibility-tree/index.md)
- [Semantic HTML](https://seo-geo-glossary.com/en/glossary/semantic-html/index.md)
- [Viewport meta tag](https://seo-geo-glossary.com/en/glossary/viewport-meta-tag/index.md)

## Sources

- [Introduction to Web Accessibility – W3C WAI](https://www.w3.org/WAI/fundamentals/accessibility-intro/)
- [WCAG 2 Overview – W3C WAI](https://www.w3.org/WAI/standards-guidelines/wcag/)
- [Guidance on Web Accessibility and the ADA – ADA.gov](https://www.ada.gov/resources/web-guidance/)
- [Fact Sheet: Final Rule on Accessibility of Web Content (State and Local Governments) – ADA.gov](https://www.ada.gov/resources/2024-03-08-web-rule/)
- [§ 1 BFSG (Barrierefreiheitsstärkungsgesetz, implementing Directive (EU) 2019/882) – Gesetze im Internet (German)](https://www.gesetze-im-internet.de/bfsg/__1.html)
- [Accessibility – MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/Accessibility)
- [Decorative Images – W3C WAI Images Tutorial](https://www.w3.org/WAI/tutorials/images/decorative/)
- [Understanding SC 1.4.3 Contrast (Minimum) – W3C WAI](https://www.w3.org/WAI/WCAG22/Understanding/contrast-minimum.html)
- [Links crawlbar machen – Google Search Central](https://developers.google.com/search/docs/crawling-indexing/links-crawlable)

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Last updated: October 8, 2026
URL: https://seo-geo-glossary.com/en/glossary/web-accessibility/