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by Wilco Fiers (Deque Systems Europe)

Web accessibility is a hot topic these days. The EU’s Web Accessibility Directive requires governments throughout the EU to build websites and apps that are accessible for people with disabilities. Over the next few years, the European Accessibility Act will mean similar requirements will apply to private businesses as well.

All this accessibility legislation is based on the same international standard; the Web Content Accessibility Guidelines (WCAG) [L1]. WCAG is developed and maintained by the World Wide Web Consortium (W3C). WCAG 2.0 is internationally recognised as an ISO standard, and WCAG 2.1 was incorporated in the EN 301 549. One of WCAG’s biggest strengths is that it is written in a technology-neutral language. This allows it to apply to technologies that came out after WCAG was published. It also makes it useful for non-web technologies. Even though WCAG was not written to comprehensively apply to mobile apps, the EU’s guidelines for mobile app accessibility are largely from WCAG.

Transposing Web Accessibility
Taking the technology-neutral language of WCAG and working out what it means for specific technologies requires a transposition. For example the term “text alternative” in WCAG is something called “accessible name” in the lingo of web pages. As anyone who speaks more than one language knows, there are often different ways you can transpose something. This is also the case when translating WCAG and applying it to a particular technology.

There are different ways to explain how WCAG should be applied to specific technologies. These differences are small and get into nuances of how specific technologies work. These differences show up when you start comparing accessibility tests done with different tools [1], or by accessibility experts from different organisations [2].

With different countries introducing their own legislation on web and mobile accessibility, even though they all use the same WCAG requirements, because of these transpositions, there are subtle differences in what regulators in different countries consider a compliant website. For companies that work internationally, this creates some uncertainty about the compliance of their website across different countries. When it comes to knowing your organisation complies with legislation, “probably” is not a satisfactory answer.

Harmonised Web Accessibility
To try and address this challenge, the W3C has developed rules and examples that document how WCAG should be applied to particular technologies. These are known as Accessibility Conformance Testing (ACT) Rules [3, L2], or more specifically, WCAG Test Rules when it comes to rules and examples written for WCAG.

The Web Accessibility Initiative (WAI) is an initiative of the W3C. As part of the WAI-Tools project [L3], co-funded by the European Commission (EC), a partnership led by the W3C developed 95 rules, and more than 1,000 examples of how to apply WCAG to HTML. This covers many of the most common types of accessibility problems. Most of those rules are focused on bringing greater consistency in the way automated accessibility tools recognise issues. Various popular accessibility tool vendors have started to apply these rules already. However, it has been difficult to track how consistently this has been done.

Another common challenge in web accessibility is knowing what different accessibility tools are capable of testing, and understanding their differences. The Web Accessibility Initiative - Communities of Practice (WAI-CooP) project, another EU funded project, aims to bring clarity to this topic.

ACT Implementation Matrix
WAI-CooP [L4] is a Coordination and Support Action project, co-funded by the European Commission (EC). WAI-CooP is a project led by the ERCIM, host of W3C Europe, which supports implementation of the international standards for digital accessibility. WAI-CooP:

  • establishes international vendor-neutral overviews on available training, tools, and resources
  • analyses technological advancements and coordinates with relevant research and development
  • provides opportunities for key stakeholders to share resources and to exchange best practices.

Part of WAI-CooP’s vendor-neutral overview includes creating an implementation matrix for accessibility tools and methodologies that have implemented ACT rules. Vendors can run their tools and methodologies on the 1,000+ examples and post their results online. This implementation matrix groups tools and methodologies into three categories:

  • Evaluation methodologies: Step-by-step instructions on how to test accessibility
  • Semi-automated tools: Tools that combine user input and automated testing to test accessibility
  • Automated tools: Tools that automatically test accessibility.

It is worth noting that this ACT implementation matrix is only designed to track the consistency of accessibility tools and methodologies with ACT rules. ACT rules are not exhaustive though. Tools and methodologies may, and likely do include tests that either aren’t covered by ACT, or where the transposition of WCAG differs from that of the ACT rules.

The ACT implementation matrix is not an endorsement of any particular accessibility tool or methodology by the W3C. It is based on data published by accessibility vendors. That is why vendors that have not published detailed test results are not part of the ACT implementation matrix. The data is taken as-is, and often cannot be verified by the W3C.

ACT Rules in Action
You can find information about which vendor has implemented which rule on the WCAG 2 test rules pages on the W3C website [L5]. A general overview per tool and methodology is also under development. It is expected to go live in the second quarter of 2022. This overview will also include a high-level summary of the number of rules each tool and methodology has implemented.


[1] T. Frazão, C. Duarte: “Comparing accessibility evaluation plug-ins”, in Proc. of the 17th Int. Web for All Conference (W4A ‘20), Article 20, 1–11, 2020.
[2] Y. Yesilada, G. Brajnik, S. Harper: “How much does expertise matter? A barrier walkthrough study with experts and non-experts”, in Proc. of the 11th Int.ACM SIGACCESS Conf. on Computers and Accessibility (Assets ‘09), 203–210, 2009.
[3] W. Fiers, et al.: “Accessibility Conformance Testing (ACT) Rules Format 1.0”, World Wide Web Consortium (W3C).

Please contact:
Wilco Fiers
Deque Systems Europe B.V., The Netherlands
This email address is being protected from spambots. You need JavaScript enabled to view it.

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