Techniques for WCAG 2.0

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G181: Encoding user data as hidden or encrypted data in a re-authorization page

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.0 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.0.


Pages that require user authentication where the time available for submitting data is limited.

This technique relates to:


Web servers that require user authentication often terminate the session after a set period of time if there is no activity from the user. If the user is unable to input the data quickly enough and the session times out before they submit, the server will require re-authentication before proceeding. When this happens, the server passes (as hidden data) the information from the form into the page that is used for re-authentication. Then, when the user re-authenticates, the server can use the information passed on from the re-authentication page to submit the form directly or to present a page that includes the data that is to be submitted for review. In this technique, the server does not have to store any user-submitted data on server. This is an important technique for those cases where it is either illegal or a security risk for the server to store information temporarily. It also is useful in that it frees the server from having to maintain the stored information and reconnect it with the newly authenticated session.

Note: If the data users are submitting is sensitive or presents a security risk, authors should consider the process used to pass the data to the re-authentication page and, after re-authentication, to the page that will process the original data in order to ensure that the data is protected.




On a site that requires user login to submit data:

  1. Log in and begin the timed activity.

  2. Allow the session to time out.

  3. Submit the data.

  4. Re-authenticate.

  5. Check that the process can continue and be completed without loss of data, including the original data and any changes made after re-authentication.

  6. Check that the process used to save the information submitted in step 3 is not stored on the server. (Note: This requires knowledge of the technology and features used to implement the technique.)

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.