In addition to being grouped by principles, WCAG is also grouped by level of conformance. These levels are described by W3C as follows:
Conformance levels can be thought of in terms of their importance toward removing barriers with Level A being the most important. It is helpful to think of levels as things you must do, should do, and could do.
- Level A: These issues must be resolved or some group will not be able to access the content. The issues at this level represent significant barriers that may not be overcome with work-arounds. An example of a Level A barrier is missing alternative text to describe an image. There is little a blind person can do on their own to understand the content of an image without a text description.
- Level AA: These issues should be resolved or some group will find it difficult to access or use the content. These issues can often be circumvented with some effort, but will make using or understanding web content more effortful. An example of a Level AA barrier is not being able to follow the focus of the cursor when navigating through content with a keyboard. For a person with low vision navigating with a keyboard, or a fully able keyboard user for that matter, navigating through content can be very difficult if one cannot see where the cursor is located and is unable to tell when to press the Enter key to activate a link or button.
- Level AAA: These issues could be resolved to improve usability for all groups. Web content may be technically accessible, but usability can be improved by resolving these issues. An example of a Level AAA barrier would be presenting acronyms or abbreviations without providing their full wording. For a person who is blind, an acronym read by a screen reader may sound like gibberish. For a fully able user who is not familiar with a short form, an acronym or abbreviation may have no useful meaning, at least not without having to search out the meaning elsewhere.
Selecting a Level of Conformance
While Level A conformance is an honourable accomplishment, and will allow most people to access the content of a website, it is generally considered “minimal conformance.” If you are working with a limited budget (or no budget) this may be an acceptable level of accessibility, but it is generally accepted that most sites should strive for Level AA, and perhaps conform with a few of the Level AAA success criteria (defined below).
If you are working on a new website, Level AA should be the goal from the start. Assuming the developers know what needs to be done, there is very little extra effort required to jump from Level A to Level AA. If you are working with an existing site that is receiving an accessibility retrofit, then you may want to first aim for Level A, then with time resolve all Level AA issues. Generally speaking it is less costly to build a site to be accessible from the start, than it is to build a site and retrofit it later to conform.
Level AAA conformance is unattainable for many websites. While it is possible to conform with some of the requirements at this level, they can often be counter-productive or unnecessary. Take for instance the reading level requirement (WCAG success criterion 3.1.5). Public sites will want to strive to meet this guideline, to reach the broadest audience possible by reducing the reading level, but for other sites that focus on a particular, perhaps highly-educated audience, it may be impossible or even inadvisable to comply with this requirement. Imagine an advanced course in biomechanics written at a lower-level secondary school reading level required to satisfy this guideline. If it were possible, replacing the advanced terminology and jargon with low level paraphrasing would likely make the content unusable by the intended audience.
Success Criteria and Techniques
Success criteria are essentially accessibility requirements. For example, the success criterion for an image conforming with guideline 1.1 (see below), is providing an equivalent text alternative. Note the success criterion does not specify any technology-specific solution or strategy on how that equivalent text should be provided.
Alternatives for an image can take different forms, hence the techniques for satisfying success criteria. For success criterion 1.1.1 possible techniques might include providing alt text, including an image caption, or describing the image in the surrounding text and referring to the description in the alt text for the image. Each of these techniques potentially satisfies the requirements or success criteria of Guideline 1.1.
You may also notice techniques are grouped into Sufficient Techniques and Advisory Techniques. Sufficient techniques are those that reliably satisfy success criteria, while an advisory technique may not reliably satisfy success criteria but may be beneficial for improving usability or improving accessibility for specific users. Developers should apply sufficient techniques to satisfy success criteria, and where feasible also apply advisory techniques to improve accessibility or usability further.
There is a third category of techniques called Failures. These are not techniques to satisfy success criteria, but rather techniques that introduce barriers and thus should be avoided.
Other Conformance Considerations
In addition to meeting all the Level A or AA or AAA requirements before being able to claim conformance at one of these levels, there are other conformance requirements, listed here:
- Full pages: Conformance applies to full web pages only. It cannot apply to parts of pages.
- Complete processes: When a conformance claim is being made on a collection of pages that make up a web application, for instance, all pages in the collection must conform. If one were to claim “the discussion forum conforms at Level AA,” all aspects of the forum must conform, from logging in, to reading posts, to posting new messages, and so on.
- Accessibility supported: Techniques to implement accessibility requirements are done in a way that is supported by assistive technologies. For instance, a linked image that is clicked to open a feature that does not have alt text to describe the function of the image, but does include text nearby that says “click the button to open the feature,” would not be accessibility supported even though the image has been described with text. The image has not been described in a way that assistive technologies can make use of. Adding alt text to the image in this case would be considered accessibility supported, because assistive technologies can read alt text. Accessibility support is a very complex issue with many grey areas. Read through “Understanding Accessibility Support” for a discussion of other things to consider when assessing accessibility support.
- Non-interference: When non-accessible technologies are used and accessible alternatives are provided, the inaccessible version must not interfere with access to the accessible version. For instance, an embedded Flash object may have a link to an accessible HTML version on the page following the object. If while navigating through the page by keyboard or using an assistive technology, the cursor becomes trapped in the Flash object, it is interfering with the accessible version that follows. In this case, even though an accessible version is provided, it cannot be accessed; thus, the page does not conform. If a bypass link were provided to skip over the Flash object, and users were able to back out of the object, the page would conform. Ideally, the Flash object should be created in a way that does not trap the cursor.
Making Conformance Claims
Once a website has addressed all the issues required for a certain level of conformance, it may be desirable to “claim” conformance, though there is no requirement that a claim be made in order to conform.
Basic Conformance Claim
A basic claim must include the date the site was judged to be conformant. Because web content tends to change over time, conformance can typically only be claimed for a specific date (with exceptions such as numbered versions of web software). The basic claim must also include the specification or standard the site is claiming conformance with, and must include the level of conformance. A basic conformance claim may look like the following:
A conformance claim can be more extensive than just a basic claim like that described above. It can also provide documentation about the accessibility features found on a site, so those accessing the site with assistive technologies can read about these features rather than having to discover them on their own. This documentation is often found linked prominently in the navigation elements of a website, usually near the start of a page so it is easily found by assistive technology users, and is often labelled “Accessibility” or “Accessibility Statement.”
If the conformance claim does not apply to the whole site (e.g., there may be some older content that remains inaccessible), the scope of the claim should also be specified. For instance, add to the basic claim above, “…for any content added to the site after January 1, 2012.” The claim can also list known issues, if there are areas of the site that are known to be inaccessible, perhaps because there isn’t a suitable accessible alternative to a particular technology being used. For example, “…the video conferencing area of the site remains non-conformant due to the lack of an alternative accessible conferencing system.”