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Remember the guidelines where divided into different success criteria? Nice. Those success criteria are classified into 3 levels.

  • Single-A (A): the lowest
  • Double-A (AA): the medium
  • Triple-A (AAA): the highest

They are similar to the WCAG 1.0 checkpoints’ priorities, but WCAG 2.0 stresses that all success criteria are important: Lowest level enables the access to the webpages, and highest level enables their usability.

To decide which level is each criterion, the WAI has established these questions:

  • Is this success criterion essential? If this criterion not met, the user agents (including assistive technology) cannot reproduce the webpage.
  • Is this success criterion applicable for every website, despite its content, type of content, technology used…?
  • Can the content creators be able to learn how to meet this success criterion? The WAI has establised one week or less to acquire these skills.
  • How will this success criterion limit the functions or “look & feel” of the page? This includes functionality, presentation, freedom of expression (everyone, including not tech-people should contribute), design or aesthetic.
  • Is there an alternative, indirect way if the success criterion is not met?

One great point on WCAG 2 is that they provide an official way of testing each criterion. We will see how can we test them later.

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Introduction to Accessibility Evaluation


The WCAG 1.0 did not have any official way to audit the accessibility of the websites. This led to the creation of different non-official evaluation methodologies. For example, the European Union founded the Unified Web Evaluation Methodology or UWEM, which was never adapted to the new WCAG 2.

This time the W3C has not forgot this issue and have developed the Website Accessibility Conformance Evaluation Methodology or WCAG-EM, albeit six years after the publication of the WCAG 2. This document is still a “Note”, not an official “Recommendation”, but we can consider it a stable reference.

If you have ever used the UWEM, they were divided into two documents: one with the core procedure, and another with the tests you should perform to verify each guideline. The WCAG-EM only provides the core procedure. We will explain it in the next post ‘The evaluation procedure’.

To verify each succes criterion, you have to follow the Techniques documentation. For example, to test if a webpage conforms to the succes criteria 1.2.3, 1.2.5 and 1.2.7 (all related to “Audio-descriptions”), you have to follow the procedure of the technique G8: Providing a movie with extended audio descriptions. There are 591 techniques and procedures to take, so have a seat while you are evaluating a website, and it is absolutly out of the scope of this tutorial to explain each procedure.

Finally, bear in mind that with the WCAG-EM we are only evaluating a selection of pages of your website, so be careful what you state in your conformance claim. Remember that the WCAG 2 considers a website as a whole: full pages, processes, functionalities…

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