The WCAG has gone through several updates since the publication of 1.0 in 1995. WCAG 1.0 has since been superseded by WCAG 2.0 and its subsequent versions.
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WCAG 2.0 - published 11 December 2008.
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WCAG 2.1 - published on 5 June 2018 and is now the W3C recommended version.
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WCAG 2.2 - published on October 5th 2023.
The introduction of the new iterations adds new requirements.
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WCAG 2.0 had 61 success criteria.
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WCAG 2.1 introduced 17 more success criteria to address mobile accessibility, people with low vision, and people with cognitive and learning disabilities.
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WCAG 2.2 expands on 2.1 with nine new success criteria, plus an update to one, with the goal of making content more accessible to a wider range of users.
The newer versions of WCAG 2 are backward compatible, meaning that all requirements in 2.0 are included in 2.1 and 2.2. So all content that conforms with the latest version of the guidelines should conform with the older versions too.
The current standing WCAG versions 2.0 and 2.1 are categorized according to four principles, perceivable, operable, understandable, and robust (POUR).
Perceivable
Elements that convey information, or website user interface components must be presented in a way that users are able to find, process, and understand.
Operable
All functionality and navigation on the website should be usable.
Understandable
Information and the operation of the user interface must be clear and understandable to users of all abilities.
Robust
The website should be capable of adapting and developing itself to support a variety of current and potential future user agents, including assistive technologies.
Under each principle are testable success criteria that provide recommendations on how to make digital content more accessible. The success criteria are classified by three levels — A, AA, and AAA — with A being the most basic level of WCAG compliance, and AAA being the strictest.
Learn more about the elements of WCAG and how to comply with its success criteria
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On 21 January 2021, the WAI released the first working draft of the WCAG 3.0. WCAG 3.0 is planned to be a major revision with the intention to make the guidelines more user-friendly than the WCAG 2 iterations, and more flexible, covering even more content, apps, and tools, as well as organizations and disabilities. WCAG 3.0 is still in development and is not expected to be finalized for the next few years.