About WCAG
Sufficient and Advisory Techniques
For each success criteria in WCAG, there are supporting techniques available that provide potential solutions or strategies that can be used to ensure barriers are removed in web content. The techniques documents continue to evolve over time (i.e., informative). New techniques are added as technology and our understanding of barriers and solutions improve. This is unlike the WCAG specification itself, which stays stable (i.e., normative) until a new version of the specification is created.
While techniques listed in the WCAG supporting documents are recommended, strategies for eliminating barriers are not required per se. There may be several techniques available to address a success criteria, or there may be techniques available that are not listed in the supporting documents. As such, techniques are not a requirement; success criteria are. Any technique can be used that reliably removes barriers associated with a particular success criterion.
There are two types of techniques that can be used to remove barriers: sufficient techniques and advisory techniques.
Sufficient Techniques
Sufficient techniques are techniques known to reliably address particular barriers. They are typically technology-specific, particular techniques with a related prefix for resolving HTML accessibility (H), scripting accessibility (SCR), Flash accessibility (FLASH), or one of the other technologies outlined in the following list:
- General (G)
- HTML (H)
- CSS (C)
- Client Side Scripting (SCR)
- Server Side Scripting (SVR)
- WAI-ARIA (ARIA)
- Flash (FLASH)
- Failures (F)
- PDF documents (PDF)
- Silverlight (SL)
- SMIL (SM)
- Plain-Text (T)
An example of a sufficient technique for Guideline 1.1, Success Criteria 1.1.1 Non-text Content, is technique “H37 Using alt attributes on img elements.” Adding alt text to an image that requires a short description is sufficient to make the meaningful information in the image accessible. But also, “ARIA6: Using aria-label to provide labels for objects” is listed as a sufficient technique for this success criterion. While the latter technique may be sufficient for those using current technology, there is a possibility, for those using an older browser or assistive technology (AT), that the WAI-ARIA solution may not be supported by their AT. That is, despite being a sufficient technique, it is still a good idea to include some redundancy where newer solutions are being applied. An example of this backwards compatibility is using both alt text and aria-label to provide image descriptions. If aria-label fails, the alt text will be read in its place. This is sometimes referred to as “graceful degradation.”
Note: Don’t be too concerned about understanding WAI-ARIA techniques at this point. These are typically techniques web developers would apply, or it may be applied behind the scenes by authoring tools when creating web content. For example, consider the task of adding alt text to an image you should understand (i.e., an image that is not decorative). The alt text code will look like the example below when presented in the HTML of a web page. It may be added to images through a text, alt, or title field in the authoring tool used to insert the image into a web page.
Technical:
<img src="mycat.jpg" alt="My cat Bob relaxing in the sun" / >
Suggested Reading: See techniques for Success Criteria 1.1.1 and examine the other techniques associated with this success criteria in Guideline 1.1.
Advisory Techniques
Advisory techniques may not reliably address barriers as can sufficient techniques, but they do address a particular barrier for particular people.
An example of an advisory technique might be “C22: Using CSS to control visual presentation of text” for Success Criteria 1.3.1 Info and Relationships. While this technique can be used to style text with various sizes, fonts, or indentations to represent document structure (the appearance of headings and subheadings), the visual appearance of the content will not be sufficient for those who cannot see the visual presentation. As a result, this technique needs to be used in addition to a sufficient technique that adds the structural semantics provided by the HTML heading elements, H1 to H6 (H42: Using h1-h6 to identify headings).
Suggested Reading: See techniques for 1.3.1 Info and Relationships for more about sufficient and advisory techniques for this success criteria.
A Third Category of Techniques
There is a third category of techniques called failures. These are not techniques that could be used to resolve potential barriers. Rather, failures are techniques that, when used, potentially introduce barriers. Techniques listed in this category should be avoided.
An example of a failure is “F43: Failure of Success Criterion 1.3.1 due to using structural markup in a way that does not represent relationships in the content.” In this case, a web author or developer uses HTML heading markup to make text larger. As a result, the large text becomes part of the document’s topic structure. When read by assistive technologies, the text is announced as a heading, which may result in confusion since a heading structure is presented where none is expected. In a case like this, the C22 advisory technique mentioned above should be used to size the fonts instead of using the structural markup and larger text provided by HTML headings.
Suggested Reading: Read through the Failures for Success Criteria 1.3.1 Info and Relationships (scroll down to find them) to develop a sense of the type of strategies that content authors and web developers may use to create potential barriers.