Without naming any names – because it doesn’t really matter which tool it is – an accessibility overlay is a tool that fundamentally harms the future of web site accessibility. The nature of accessibility testing is to expose issues to a human being who can then act on those issues. An accessibility overlay, by nature, avoids exposing what problems it has addressed to a human being.

This is a crucial difference that has a long-term impact on the accessibility of the entire internet. When a tool provides feedback to a person for them to act on, that is education. Somebody has to work with that data, look at the source and interaction, and take action. In that process, they will learn more about what it takes to make a website accessible, and will hopefully make the same mistakes less frequently in the future.

An accessibility overlay affords no such benefit.

Training is about Education

Testing and training services helps to improve the overall access to digital content across every environment the trainees touch. An accessibility overlay impacts only the environment where it is applied, with no possibility of a bridge to other accessibility benefits.

When your business is selling an accessibility overlay, your business model depends on other people not learning more about accessibility. If people learn how to implement best practices on a website, or how to test for those characteristics, then they will not need you.

This is, of course, also true for people who teach accessibility or who provide accessibility audits. If you do your job well, people no longer need you. If that happened, most people working in accessibility would consider it a monumental success.

Better Decision Making for the Future

In almost every training I’ve ever done, I talk about decision making. I tell people that many aspects of accessibility are subjective. What matters to me is that they think about their options and make a choice that is conscious of the users of their site. They will not always make the best choice, and they will not always consider all of their users. But every time a designer or developer goes through that process, they will understand the user experience a little bit better.

Using an overlay takes away choices and decision making. If the overlay confers any additional accessibility, it does it thoughtlessly, based on some set of complex rules. The development team doesn’t learn anything from the process. In order to make their next site accessible, they pay the overlay company more money; and this cycle has no end.

If the decisions made by the overlay are bad, there is no path to rectify those decisions.

An Overlay Cannot Solve All Problems

Let’s briefly consider the hypothetical best-case situation. We’ll hypothesize an overlay is able to effectively solve every accessibility problem that can be resolved without human intervention. That caveat “without human intervention” is a big one. Only about 25% of accessibility problems are resolvable – or even detectable – in this manner. This leaves an enormous number of problems on the table, and provides no long-term educational benefits. The site will still need a professional audit to identify and resolve all the remaining problems.

So, after all that, assuming the best case scenario for our accessibility overlay, our accessibility consultants are still in business. But if an overlay engages in deceptive marketing that states or implies their product can solve 100% of accessibility problems, this will cause the accessibility consulting business to suffer. It increases the number of business owners vulnerable to lawsuits because they believe that they have resolved their problems and increases the frustrations of people with disabilities trying to use those websites.

Sam Evans put the concept that I’ve elaborated with excessive verbosity in a succinct and elegant statement on Twitter: