# WCAG

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: Web Content Accessibility Guidelines

The **WCAG** (Web Content Accessibility Guidelines) are the W3C's technical standard for accessible web content. They are developed by the Web Accessibility Initiative together with organizations and experts worldwide.

## Which versions and levels exist?

| Version | Published |
|---|---|
| WCAG 2.0 | December 11, 2008 |
| WCAG 2.1 | June 5, 2018 (updated edition May 6, 2025) |
| WCAG 2.2 | October 5, 2023 (updated edition December 12, 2024) |

Each version adds success criteria without changing existing ones, so content that conforms to WCAG 2.2 also conforms to 2.1 and 2.0. WCAG 2.2 marks criterion 4.1.1 Parsing as obsolete. WCAG 2.2 is also the international standard ISO/IEC 40500:2025, and WCAG 3 is still a working draft.

Success criteria have three conformance levels. A is the lowest, AA the middle and AAA the highest.

## What are the principles?

WCAG 2.2 has 13 guidelines under four principles. Content has to be perceivable, operable, understandable and robust, abbreviated POUR.

## How does law refer to WCAG?

WCAG is a standard and becomes binding through laws that refer to it. For example, a 2024 US Department of Justice rule under Title II of the ADA sets WCAG 2.1 Level AA as the technical standard for web content of state and local governments, with compliance dates in April 2027 and April 2028 after an extension announced in 2026.

This is not legal advice.

## Example

Success criterion 1.1.1, Non-text Content (Level A), requires a text alternative for non-text content, for instance an `alt` attribute on an image.

```html
<img src="logo.svg" alt="Example Inc. logo">
```

## Common mistakes

- **Images without a text alternative.** Success criterion 1.1.1 (Level A) requires a text alternative for non-text content.
- **Aiming for Level AA but skipping Level A.** The higher conformance level includes the lower ones, so the Level A criteria are part of it.

## FAQ

**Is WCAG mandatory?**
Only where a law or regulation requires it.

**Which level do most laws ask for?**
The ADA rule cited above names Level AA. Other laws differ.

## Related terms

- [Web accessibility](https://seo-geo-glossary.com/en/glossary/web-accessibility/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)

## Sources

- [WCAG 2 Overview – W3C WAI](https://www.w3.org/WAI/standards-guidelines/wcag/)
- [Web Content Accessibility Guidelines (WCAG) 2.2 – W3C Recommendation](https://www.w3.org/TR/WCAG22/)
- [Web Content Accessibility Guidelines (WCAG) 2.1 – W3C Recommendation (edition of 6 May 2025)](https://www.w3.org/TR/WCAG21/)
- [Fact Sheet: Final Rule on Accessibility of Web Content – ADA.gov](https://www.ada.gov/resources/2024-03-08-web-rule/)

---

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