UKOLN AHDS Use of Automated Tools For Testing Web Site Accessibility

Accessibility And Web Sites

It is desirable to maximise the accessibility of Web sites in order to ensure that Web resources can be accessed by people who may suffer from a range of disabilities and who may need to use specialist browsers (such as speaking browsers) or configure their browser to enhance the usability of Web sites (e.g. change font sizes, colours, etc.).

Web sites which are designed to maximise accessibility should also be more usable generally, (e.g. for use with PDAs) and are likely to be more easily processed by automated tools.

Accessibility Testing Tools

Although the development of accessible Web sites will be helped by use of appropriate templates and can be managed by Content Management Systems (CMSs), there will still be a need to test the accessibility of Web sites.

Full testing of accessibility with require manual testing, ideally making use of users who have disabilities. The testing should also address the usability of Web sites as well as its accessibility.

Manual testing can however be complemented with use of automated accessibility checking tools. This document covers the use of automated accessibility checking tools.

Accessibility Guidelines

The W3C WAI (Web Accessibility Initiative) have developed guidelines on the accessibility of Web resources. Many institutions are making use of the WAI guidelines and will seek to achieve compliance with the guidelines to A, AA or AAA standards. Many testing tools will measure the compliance of resources with these guidelines.

Examples Of Automated Accessibility Checking Tools

The best-known accessibility checking tool was Bobby which was renamed as WebXact, a Web-based tool for reporting on the accessibility of a Web page and its compliance with W3C's WAI guidelines. However this tool is no longer available.

HiSoft's Cynthia Says provides an alternative accessibility and Web site checking facility - see <>.

Note that it can be useful to make use of a multiple checking tools. W3C WAI provides a list of accessibility testing tools at <>.

Typical Errors Flagged By Automated Tools

When you use testing tools warnings and errors will be provided about the accessibility of your Web site. A summary of the most common messages is given below.

HTML resources must contain a DOCTYPE at the top of the HTML file, which defines the version of HTML used. To provide compliance with HTML standards this must be provided. Ideally this will be provided in the HTML template used by authors.
No Character Encoding
HTML resources should describe the character encoding of the document. This information should be provided. Ideally this will be provided in the HTML template used by authors.
No ALT Tags
ALT tags are used to provide a textual description of images. In order to comply with HTML standards ALT tags must be provided for all images.
Use Relative Sizes And Positioning Rather Than Absolute
Many HTML features can accept relative or absolute size units. In order to ensure that resources can be sized properly on non-standard devices relative values should be used.
Link Phrase Used More Than Once
If multiple links on a page have the same link text the links should point to the same resource.


As mentioned previously, automated testing tools cannot confirm that a resource is accessible by itself - manual testing will be required to complement an automated approach. However automated tools can be used to provide an overall picture, to identify areas in which manual testing many be required and to identify problems in templates or in the workflow process for producing HTML resources and areas in which training and education may be needed.

Note that automated tools may sometimes give inaccurate or misleading results. In particular:

Use Of Frames
HTML resources which use frames may be incorrectly analysed by automated tools. You should ensure that the frameset page itself and all individual framed pages are accessible.
Use Of Redirects
HTML resources which use redirects may be incorrectly analysed by automated tools. You should ensure that the original page itself and the destination are accessible. Remember that redirects can be implemented in a number of ways, including server configuration options and use of JavaScript, <meta> tags, etc. on a Web page.
Use Of JavaScript
HTML resources which use JavaScript may be incorrectly analysed by automated tools. You should ensure that the source page itself and the output from the JavaScript are accessible.