4. Robust
4.1 Compatible (Level A and AA)
Contents
Guideline 4.1 Compatible
Maximize compatibility with current and future user agents, including assistive technologies.
Why is compatibility important?
The goal of Guideline 4.1 is to ensure that web pages display correctly and work as the author intends in the following cases:
- All current and future browsers, web-enabled devices, and assistive technologies
- All current and future assistive technologies
Not all users have up-to-date technologies. Compatible web pages also work reasonably well in older and obsolete browsers, web-enabled devices, and assistive technologies. Obviously, not all features available on modern websites are compatible with older technologies.
Guideline 4.1 requires web authors to confirm the following:
- Ensure that code does not “break” or otherwise impede assistive technologies
- Expose information in standard ways so that assistive technologies can recognize and interact with content
Web technologies change quickly, and assistive technology developers are constantly playing catch-up. When web authors code according to specification, they maximize the chances that assistive technologies will work seamlessly with present and future technologies.
Success Criterion 4.1.1 Parsing
Level A
In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.
Note: Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute-value quotation mark are not complete.
Parsing Explained
Ensure web pages conform to all markup language specifications.
Conforming to SC 4.1.1 ensures that browsers, web-enabled devices, and assistive technologies interpret, parse, and display content accurately. Improper markup may cause content to display differently in different browsers or devices, display incorrectly, not display at all, or be inaccessible to assistive technologies.
An easy way to test SC 4.1.1 is to use a validation tool, such as the W3C Markup Validation Service. A good validator will detect incomplete start and end tags, missing quotation marks, problems with attributes, duplicate IDs, and more.
Toolkit: Add the W3C Markup Validation Service to your toolkit and use it to test how well websites comply with the HTML5 standard.
Suggested Reading:
Success Criterion 4.1.2 Name, Role, Value
Level A
For all user interface components (including, but not limited to, form elements, links, and components generated by scripts), the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically set; and notification of changes to these items is available to user agents, including assistive technologies.
Note: This success criterion is primarily for web au