2003 Conference Proceedings

Go to previous article 
Go to next article 
Return to 2003 Table of Contents 


Wendy Chisholm (W3C/WAI)
Ben Caldwell
Trace Research and Development Center


An overview of the progress on WCAG 2.0 and how it builds on WCAG 1.0. Demonstrates applicability of WCAG 2.0 to a range of Web technologies.


Since the release of the Web Content Accessibility Guidelines 1.0 (WCAG 1.0) [WCAG10] as a World Wide Web Consortium (W3C) Recommendation in May 1999, the WCAG Working Group (WCAG WG) has collected feedback about the usability, understandability, and applicability of WCAG 1.0 documents and has utilized that feedback in advancing the development of WCAG 2.0 [WCAG20].

This paper provides an overview of the progress that has been made in the evolution of WCAG 2.0. While the WCAG WG has used the feedback from WCAG 1.0 to set requirements that WCAG 2.0 must meet, in this paper we focus on applying WCAG 2.0 to a variety of technologies.

Please note that the differences described in this paper are representative of the W3C Working Draft of WCAG 2.0 as of October 2002. As a draft document, it is subject to continued change based on feedback and review we receive and may be updated, replaced, or obsoleted by other documents at any time. This work is part of the Web Accessibility Initiative (WAI) Activity of the W3C.

Why WCAG 2.0?

The primary goal of WCAG 2.0 is the same as WCAG 1.0: to promote accessibility of Web content.

The overall goal is to create Web content that is perceivable, operable, navigable, and understandable by the broadest possible range of users and compatible with their wide range of assistive technologies, now and in the future.[WCAG20]

While the goals are similar, there are a number of significant differences between WCAG 1.0 and WCAG 2.0. However, the WCAG WG is working carefully to enable organizations and individuals that are currently using WCAG 1.0 (which remains stable and referenceable at this time) to ensure that they will eventually be able to make a smooth transition to WCAG 2.0.

To ensure that WCAG 2.0 will promote accessibility of Web content effectively, the WCAG WG outlined the following requirements in "Requirements for WCAG 2.0" [WCAG20-REQ]:

  1. Ensure that requirements may be applied across technologies
  2. Ensure that the conformance requirements are clear
  3. Ensure that the deliverables are easy to use
  4. Write to a more diverse audience
  5. Clearly identify who benefits from accessible content
  6. Ensure that the revision is "backwards compatible"

Differences Between WCAG 1.0 and WCAG 2.0

The difference that is most apparent is the change in structure. WCAG 1.0 was organized into 14 Guidelines and 65 Checkpoints. Currently (October 2002), WCAG 2.0 has 5 Guidelines and 21 Checkpoints yet it addresses accessibility requirements as comprehensively as does WCAG 1.0. Additionally, each WCAG 2.0 Checkpoint has three levels of Success Criteria.

The reduced number of Guidelines and Checkpoints is intended make the document more approachable. By generalizing the principles in WCAG 1.0 and removing technology-specific aspects, we were able to combine concepts that had existed separately.

An important piece of feedback we receive from people implementing WCAG 1.0, is that it can be difficult to determine if they have met the requirements. WCAG 2.0 strives to clearly describe what is required for conformance. To that end, success criteria have been constructed so that they can be reliably tested. A success criterion is considered testable if there exist, at least in principle, automated or semi-automated testing procedures that can reliably determine whether or not the requirement has been satisfied. "Additional ideas" - strategies that can not be reliably tested but should be taken into account - supplement many of the success criteria.

Another significant difference is that WCAG 2.0 requires that, in order to claim any conformance to the guidelines, it is necessary to satisfy the "Minimum Level" success criteria of every checkpoint. Minimum Level success criteria represent those aspects of the checkpoint requirements which, in the absence of a full implementation, will nonetheless offer substantial benefit to people with disabilities by removing barriers that would otherwise make it difficult or impossible to access the content. The Level 2 and Level 3 criteria build upon this functionality, making the content accessible to people who would not be able to access it, or could do so only with substantial difficulty, if only the minimum criteria had been met.

One of the primary reasons the new conformance model was introduced is that the Working Group found in working on WCAG 2.0 that WCAG 1.0 did not clearly describe some of the relationships and dependencies that exist between checkpoints. While some checkpoints simply make accessing the Web easier for some people, addressing these same checkpoints is a critical part of making the Web accessible for others. In effect, all of the checkpoints in the document fall into the "Minimum Level" category of success criteria for some people. Therefore, the group decided that all checkpoints need to include some "Minimum Level" items.

Applying WCAG 2.0 Across Technologies

As a set of guidelines that will be released after the deployment of some technologies but prior to the development of other technologies, there are a variety of issues related to the current, changing state of the world. There are three aspects to this issue:

  1. The Past: writing general principles and testable statements to older browsers and assistive technologies that some people with disabilities use.
  2. The Present: being able to give authors advice on what to do today.
  3. The Future: writing general principles and testable statements that may be applied to technologies that do not yet exist.

Most of WCAG 1.0 is applicable to current Web technologies. However, it was written primarily with Hypertext Markup Language (HTML) and Cascading Style Sheets (CSS) in mind and therefore some requirements are specific to those languages. The WCAG 2.0 Working Drafts to date do not mention solutions specific to a single Web technology. Instead, they describe solutions that are intended to be generalized across technologies, including Web applications.

The challenges and opportunities that Web authors face today are outlined in "Authoring Scenarios for Device Independence." [ASDI] Not only is a new generation of mobile technology available, but key developments such as the Semantic Web, Web Services, and speech applications are changing how people interact with information.

Another aim of WCAG 2.0 is to facilitate documentation of techniques to help authors create content on a variety of technologies that can conform to WCAG 2.0. Collaboration with the W3C Device Independence Activity, the Internationalization Activity, the Quality Assurance Activity, and the Protocols and Formats Working Group are key in ensuring we have the most up-to-date information possible. Also, where possible, we are working with the developers of the new technologies to help us write techniques. The W3C/WAI Education and Outreach Working Group will help us reach the variety of needs in the WCAG 2.0 audience by creating supplementary materials.

Implementation Testing and the W3C Candidate Recommendation Phase

To determine if we have met the goals outlined in "Requirements for WCAG 2.0" [WCAG20-REQ], we will go through an implementation testing process. In W3C terms this is the "Candidate Recommendation" status [W3C-CR]. During the implementation period, the Working Group demonstrates that each feature of the technical report has been implemented. For example, the WCAG WG might document how a variety of Web sites conform to WCAG 2.0 across a mixture of variables such as:

The "Summary implementation report for User Agent Accessibility Guidelines 1.0" (UAAG 1.0) [UAAG-IMP] provides an example of what the WCAG WG will aim to develop.


The WCAG WG is addressing the feedback received since the publication of WCAG 1.0 in WCAG 2.0. This includes ensuring the requirements may be applied across a variety of technologies, making the conformance requirements clear, making the materials easy to use, writing to a diverse audience, identifying who benefits, and creating something that does not completely change how accessible content is defined by WCAG 1.0.

To meet these goals, it is critical that the WCAG WG receive feedback from a variety of sources including Web authors, policy makers, individuals with disabilities who use the Web and developers of user agents, authoring tools and evaluation and repair tools. If you are interested in submitting feedback or contributing to the implementation testing, please contact Wendy Chisholm (wendy@w3.org), the W3C Team Contact for the WCAG WG.



"Authoring Scenarios for Device Independence," R. Lewis, ed. Informal public draft of possible W3C Note, at http://www.w3.org/2001/di/public/as/


"Summary implementation report for UAAG 1.0," J. Gunderson, I. Jacobs, M. May, eds., at http://www.w3.org/WAI/UA/impl-pr2/


"W3C Process Document," I. Jacobs, ed. Section 5.2.3 Candidate Recommendation, at http://www.w3.org/Consortium/Process-20010719/tr.html#RecsCR


"Web Content Accessibility Guidelines 1.0," W. Chisholm, G. Vanderheiden, I. Jacobs, eds. W3C Recommendation, at http://www.w3.org/TR/WCAG10/


"Web Content Accessibility Guidelines 2.0," B. Caldwell, W. Chisholm, J. White, G. Vanderheiden, eds. W3C Working Draft, at http://www.w3.org/TR/WCAG20/


"Requirements for WCAG 2.0," G. Vanderheiden, W. Chisholm, eds. W3C Working Draft, at http://www.w3.org/TR/wcag2-req/ 

Go to previous article 
Go to next article 
Return to 2003 Table of Contents 
Return to Table of Proceedings

Reprinted with author(s) permission. Author(s) retain copyright.