Techniques for WCAG 2.0

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G174: Providing a control with a sufficient contrast ratio that allows users to switch to a presentation that uses sufficient contrast


Any technology.

This technique relates to:


When the contrast between the text and its background for some portion of the page has not been designed to meet the contrast level for Success Criterion 1.4.3 or 1.4.6, it is possible to meet these guidelines using the "Alternate Version" clause in the conformance requirements (Conformance Requirement 1). A link or control on the page can either change the page so that all aspects conform, or it could take the viewer to a new version of the page that does conform at the desired level. Placing the link or control prominently on the page will assist users in accessing the conforming content readily.

For this technique to be used successfully, three things must be true:

  1. The link or control on the original page must itself meet the contrast requirement of the desired SC. (If the user cannot see the control they may not be able to use it to go to the new page.)

  2. The new page must contain all the same information and functionality as the original page.

  3. The new page must conform to all of the SC for the desired level of conformance. (i.e., the new page cannot just have the desired level of contrast but otherwise not conform).

This technique can be used to meet Success Criterion 1.4.3 by having text (or images of text) on the alternate version of the page be 4.5:1 contrast and any large text (or images of large text) be 3:1 contrast with its background. If the alternate version of the page has all text (or images of text) with 7:1 contrast and large text (or images of large text) with 4.5:1 contrast then it would satisfy both Success Criterion 1.4.3 and 1.4.6.

Note: This technique can be used in combination with a style switching technique to present a page that is a conforming alternate version for non-conforming content. Refer to C29: Using a style switcher to provide a conforming alternate version (CSS) and Understanding Conforming Alternate Versions for more information.




  1. Check that a link or control exists on the original page that provides access to the alternate version.

  2. Check that the link or control on the original page conforms to all success criteria for the conformance level being tested.

  3. Check that the alternate version meets the contrast and all other success criteria for the conformance level being tested.

Expected Results

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.

Techniques are Informative

Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.