This section contains the main explanatory content of the Understanding. It explains why the Guideline or Success Criterion exists and, at a high level, how to meet it.
The intent of this success criterion is to ensure that, if users are able to make use of content they are seeking, they do not encounter a barrier that prevents them from accessing it.
Most user interfaces are designed to help users complete tasks. However, traditionally, web security and privacy technologies intentionally introduce barriers to task completion. They require users to perceive more and to do more to complete tasks.
Many user authentication methods rely upon trying to differentiate between a human, and software (bots) that try to pose as a human. The most common way of trying to make this distinction is by the setting of tasks that rely upon human abilities, and that are almost impossible for software (bots) to perform. These methods can frequently be quite challenging for people who have a high level of relevant ability. For people who have a lower level of relevant ability, an authentication task often presents an insurmountable barrier.
An alternative user authentication method is required for users who are temporarily or permanently unable to use the primary user-authentication method. One important example is where users would be unable to use a primary user authentication method, such as when they do not have a suitable trusted device, or if they are not subscribed to or are unable to access third-party services (often part of user authentication methods), which would meet the criteria for primary user-authentication methods.
The six abilities that are referred to in the alternative success criterion are those that are frequently employed as user authentication methods. The SC asks for the availability of at least one method that does not rely upon any of these abilities being offered.
This explains how following the success criterion benefits particular types of users with disabilities.
Without this success criterion, many people cannot use an application or content at all. See Security and Privacy Technologies issue paper for the full description of this issue, and how it stops people from using web services that are often critical. Many people cannot make doctors appointments, etc., by themselves. This may be partly responsible for the reduced life expectancy of people with learning and cognitive disabilities.
With this success criterion, people who are able to use a primary user authentication method will be able to successfully complete a user authentication procedure almost irrespective of the level of their cognitive abilities. Those who have to use an alternative method will be able to successfully complete a user authentication even though they have limited levels of the cognitive abilities specified in the success criterion.
Examples in Understanding pages are normally simple lists of hand-waving examples. Sometimes, examples are instead provided in sub-sections with headings. In either case, examples should stay high-level and not get into code specifics, which is for techniques.
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See also
This section references techniques that can be used to meet the Guideline or Success Criterion. There are sub-sections for sufficient techniques, advisory techniques, and failures.
Remove any parts of the template that are not used, such as the section and heading for situations, sub-lists of techniques, or the "AND" construction. Also remove the square brackets around placeholder optional components.
Techniques that are sufficient to meet the Guideline or Success Criterion.
Techniques that are not sufficient by themselves to meet the Guideline or Success Criterion.
Same template as sufficient techniques.
Techniques that document conditions that would cause the page not to meet the Guideline or Success Criterion, even if sufficient techniques are also used.
Same template as sufficient techniques.