Overview of Web Content Accessibility Guidelines- E-book Publishing Online book Icon, Flat Computer mobile devices, blue, computer Network

The W3C WCAG guidelines were developed through an open process by the World Wide Web Consortium (W3C).  The most recent set of guidelines WCAG 2.1 was published on 5 June 2018 and are organized under 4 central principles with testable “success criteria”: Perceivable, Operable, Understandable, and Robust.  For each guideline, there are testable success criteria, which are at three levels – level A, level AA and level AAA.

The WCAG are part of a series of web accessibility guidelines published by the Web Accessibility Initiative of the W3C, the main international standards organization for the Internet. The guidelines provide a set of technical requirements for making your website, app or other digital properties accessible to people with various disability types.

The WCAG standards can be applied to technologies such as software and native mobile apps. Some examples of web-based content where WCAG is applicable include:

Pdf Logo, Document, Hyperlink, Html
  • HTML pages
  • Scalable Vector Graphics
  • Flash
  • PDF documents
  • Silverlight
  • Mobile websites.

There are three versions of WCAG : 1.0, 2.0 (replaced 1.0), and 2.1 and the release of 2.2 is expected in 2021.

WCAG 1.0

This version uses guidelines to address accessible design. These guidelines address two themes: ensuring graceful transformation, and making content understandable and navigable.

Each guideline under WCAG 1.0 has a checkpoint, which are priority 1, 2, or 3.

  • Priority 1: address criteria a web developer “must satisfy”
  • Priority 2: lists criteria a web developer “should satisfy”
  • Priority 3: supplies optional checkpoints a web developer “may address”

Because WCAG 1.0 was published in 1999, it primarily addresses HTML web pages, since that was the majority of web content at the time. It did not account for advances in technology, new software, and advanced applications of digital content.

WCAG 2.0

Web Content Accessibility Guidelines (WCAG) 2.0 defines how to make Web content more accessible to people with disabilities. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. These guidelines also make Web content more usable by older individuals with changing abilities due to aging and often improve usability for users in general.

The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall principles, general guidelines, testable success criteria and a rich collection of sufficient techniques, advisory techniques, and documented common failures with examples, resource links and code.

Anyone who wants to use the Web must have four principles that provide the foundation for Web accessibility that is: perceivable, operable, understandable, and robust. In order to meet the needs of different groups and different situations, three levels of conformance are defined (Success Criteria): A (lowest), AA, and AAA (highest)

WCAG 2.1

This is the newest release from W3C. WCAG 2.1 was initiated with the goal to improve accessibility guidance for three major groups: users with cognitive or learning disabilities, users with low vision, and users with disabilities on mobile devices. WCAG 2.1 is an extension of WCAG 2.0. It includes 17 new standards, many of these success criteria reference new terms that have also been added to the glossary and form part of the normative requirements of the success criteria.

WCAG 2.1 is developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a shared standard for Web content accessibility that meets the needs of individuals, organizations, and governments internationally.

WCAG 2.1 is backward compatible with WCAG 2.0, meaning web pages that conform to WCAG 2.1 also conform to WCAG 2.0. It follows the same structure, principles, and compliance levels as WCAG 2.0.

WCAG Principles

The W3C has arranged the Guidelines around the following four principles. These principles lay the foundation necessary for functional access to web content and web applications


Visual perception Business Organization Technology Science, Eye insight, blue, company, service

Information and user interface components must be presentable to users in ways they can perceive.

Your website/app must present information in ways that people can recognize and use, no matter how they consume content


Operable-Computer mouse Computer keyboard, computer operation, computer Network

User interface components and navigation must be operable.

Your website/app must be easy to navigate and use, no matter how someone interacts with it.


Understandable-Machine Learning Algorithms Understanding Machine Learning From Theory to Algorithms Recommender system

Information and the operation of user interface must be understandable.

Your website/app must make it easy for people to understand information and how to complete tasks.


Content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies.

Your website/app must work with different web browsers and/or assistive technologies.

WCAG Compliance: Level A vs. AA vs. AAA

WCAG 2.0 and 2.1 outline three levels of compliance. Level A is the highest priority and usually the easiest to achieve. Level AA is more comprehensive. Level AAA is the strictest, most comprehensive accessible design.

Computer Icons, light priority 1,2,3, angle

“It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.”

It is recommended, however, that web designers meet at least WCAG 2.0 Level A and aim for Level AA compliance.

Level A : The success criteria at Level A are designed to be the easiest to meet, without much impact on the website design or structure.

Level AA : Level AA requires a bit more commitment. Continuing with the theme of color, you have to ensure that all the text meets color contrast requirements. The requirement differs somewhat based on the size of the text, but it is actually pretty strict.

Level AAA : At Level AAA, the requirement is taken further with an even more strict color contrast requirement for text. Essentially you can only use very dark colors on a very light background and vice versa. Almost all colored text fails.

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