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 yo