The Web Accessibility Initiative (WAI)
Web Content Accessibility Guidelines 2.0 (WCAG 2.0)

Differences Between WCAG 1.0 and WCAG 2.0

Version 1.0 of the Web Content Accessibility Guidelines (WCAG) was a major development in making the Internet more accessible to people with disabilities. Version 2.0 builds upon this foundation, but also introduces some significant changes worth discussing.

On a practical level, some of the changes in WCAG 2.0 are subtle. For example, forms still require labels, data tables still require headers, and images still require alternative text. Web developers who currently design accessible web sites will not have to change their habits much. On the other hand, WCAG 2.0 represents a substantial shift in philosophy, which can be categorized under the headings of:

1. A principle-centered rather than technique-centered approach
2. Conformance can be reliably verified
3. A conformance scheme based on degrees of implementation rather than on types of guidelines

A Principle-centered Rather than Technique-centered Approach

The shift from technique-centered guidelines to principle-centered guidelines resulted in a reduced number of top level ideas, or principles. WCAG 1.0 had fourteen principles at the top level. WCAG 2.0 places only four principles at the top level under which more specific guidelines are organized. These four principles can each be referred to by a single keyword:

• Perceivable
• Operable
• Understandable
• Robust

Content must be made available to users in a format that they can perceive with at least one of their senses (i.e. sight, hearing, touch). It must be presented in a way that they can interact with or operate it with either standard or adaptive devices. It must be presented in a way that the user can understand or comprehend. Finally, content must be presented using technologies and interfaces that are robust enough to allow for disability access, whether natively or in alternative technologies and interfaces. Together these principles address all areas of accessibility, at least in broad conceptual strokes.

Conformance can be Reliably Verified

One of the key areas of weakness in WCAG 1.0 is that some of the requirements are somewhat ambiguous, leaving them open to interpretation. In terms of implementing WCAG 1.0, this means that one developer's method of complying with a particular checkpoint could be quite different from that of another developer. WCAG 2.0 does much to fix this problem, by requiring that compliance with a checkpoint can be unambiguously verified. This verification can be performed either through an automated, algorithm-based process or through human testing. Automated processes can verify the existence or absence of certain required elements, such as the alt attribute for images. Human testing requires a process that can be performed with high inter-rater reliability, for example by having 9 out of 10 trained individuals reaching the same conclusion about the element in question.

Whether the final version of WCAG 2.0 succeeds or not in making each guideline reliably verifiable remains to be seen, but so far it is an improvement over WCAG 1.0.

A Conformance Scheme Based on Degrees of Implementation Rather than on Types of Guidelines

WCAG 1.0 used a three-level conformance scheme in which the levels are referred to as "priorities" and each level is defined by the relative severity of the barriers the guidelines were meant to overcome. Priority 1 guidelines were meant to overcome the most severe barriers to accessibility. Priority 2 was meant to overcome moderate barriers to accessibility, and priority 3 was meant to overcome the least severe barriers to accessibility. In the words of the WCAG 1.0 authors,

[Priority 1]

A web content developer must satisfy this checkpoint. Otherwise, one or more groups will find it impossible to access information in the document. Satisfying this checkpoint is a basic requirement for some groups to be able to use web documents.

[Priority 2]

A web content developer should satisfy this checkpoint. Otherwise, one or more groups will find it difficult to access information in the document. Satisfying this checkpoint will remove significant barriers to accessing web documents.

[Priority 3]

A web content developer may address this checkpoint. Otherwise, one or more groups will find it somewhat difficult to access information in the document. Satisfying this checkpoint will improve access to web documents.

The priority-based scheme is abandoned entirely in WCAG 2.0. In its place is a conformance scheme based on the degree to which the developer implements the guidelines. In WCAG 1.0, each guidelines was assigned a priority, which meant that many of the guidelines were not considered priority 1 guidelines. Priority 2 and 3 guidelines were "less important" than priority 1 guidelines. In WCAG 2.0, each guideline is considered equally important and to have an equal priority, but each can be implemented to a lesser or greater degree or level: a minimal level of implementation, a moderate level of implementation, or a maximum level of implementation. The February 11, 2005 working draft of WCAG 2.0 states:

Level 1 success criteria:

1. Achieve a minimum level of accessibility through markup, scripting, or other technologies that interact with or enable access through user agents, including assistive technologies
2. Can reasonably be applied to all web resources.

Level 2 success criteria:

1. Increase accessibility through one or both of the following:
   1. further facilitating the ability of user agents to provide accessible content
   2. recommending content and/or presentation that provides direct accessibility without requiring users who have disabilities or their user agents to do anything different from users without disabilities or their user agents
2. Can reasonably be applied to all web resources.

Level 3 success criteria:

1. Go beyond Level 1 and 2 to increase direct and user agent enhanced accessibility.

 

By giving every guideline equal priority, WCAG 2.0 avoids one of the biggest problems with the WCAG 1.0 conformance scheme, which was that the priorities were assigned somewhat arbitrarily. For some types of disabilities, some of the priority 2 and priority 3 guidelines were absolutely necessary in order to achieve accessibility, whereas some of the priority 1 guidelines were not. For example, a person with a reading disability will benefit greatly from the priority 3 guideline to "Supplement text with graphic or auditory presentations where they will facilitate comprehension of the page," but may not benefit at all from the priority 1 guideline to "Clearly identify changes in the natural language of a document's text and any text equivalents (e.g., captions)."

Outline of the WCAG 2.0 Principles and Guidelines (So Far!)

Here is a summary of the guidelines along with their accompanying checkpoints in the February 11, 2004 working draft (not including the more detailed success criteria or any of the technology-specific techniques):

• Principle 1: Content must be perceivable.
  • Guideline 1.1 Provide text alternatives for all non-text content.
  • Guideline 1.2 Provide synchronized alternatives for multimedia.
  • Guideline 1.3 Ensure that information, functionality, and structure are separable from presentation.
  • Guideline 1.4 Make it easy to distinguish foreground information from background images or sounds.
• Principle 2: Interface elements in the content must be operable.
  • Guideline 2.1 Make all functionality operable via a keyboard or a keyboard interface.
  • Guideline 2.2 Allow users to control time limits on their reading or interaction.
  • Guideline 2.3 Allow users to avoid content that could cause photosensitive epileptic seizures.
  • Guideline 2.4 Provide mechanisms to help users find content, orient themselves within it, and navigate through it.
  • Guideline 2.5 Help users avoid mistakes and make it easy to correct them. [level 2 guideline]
• Principle 3: Content and controls must be understandable.
  • Guideline 3.1 Ensure that the meaning of content can be determined.
  • Guideline 3.2 Organize content consistently from "page to page" and make interactive components behave in predictable ways.
• Principle 4: Content must be robust enough to work with current and future technologies.
  • Guideline 4.1 Use technologies according to specification.
  • Guideline 4.2 Ensure that user interfaces are accessible or provide an accessible alternative(s)

Using WCAG 2.0 Now

Even though WCAG 2.0 is still an unfinished document, developers can still use its main concepts now. In particular, the four main principles—perceivable, operable, understandable, robust—can serve as a conceptual guide to creating all kinds of web content. Developers should always ask themselves how their content measures up to these guiding principles. Even though specific techniques will vary by technology and will evolve over time, these four principles will always be core concepts applicable to all kinds of web accessibility challenges.