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Last updated on 6/1/23

Use Automated Testing Tools


Understand the Limits of Automated Testing

Automated tools can be great as a quick check! But their capabilities are minimal. They can only test for what is machine-checkable, and even then, they can’t use their judgment to make a meaningful conclusion. For example, an automated checker can identify if an image is missing alternative text. But some content management systems will automatically use the image file name as an alt text attribute. In this case, the image would pass the check even though the description communicated to the user could be something like “IMG3334.PNG.” Hardly useful! Similarly, a checker can’t know if your heading structure is meaningful, even if it’s present. Or if the markup is appropriate for the content, as long as it’s structured correctly.

In some cases, the checker will also flag issues that, in actuality, don’t pose any barriers. For example, when I ran a WebAIM WAVE check on an OpenClassrooms page, an error came up about missing alternative text for an image link.

Error showing that one linked image is missing alternative text.
WebAIM WAVE check showing an error.

However, when I looked at where the error was occurring, I could see that this image link had an aria-label, a different method for describing assistive technologies. Because the label is there, missing alternative text isn’t an issue in this case.

Highlighted image link with an error icon and an aria-label icon with a description.
Image link with missing alternative text, which has an aria-label description instead.

There are also many accessibility issues that a checker can’t test for. For example, it won’t be able to tell you if the site is using color as a way of communicating information, or if your instructions rely on sensory cues. It’s good practice to run automated checks to see what kinds of issues come up, but then remember that all the results need to be manually checked because you’re likely to get both false positives and false negatives. And keep in mind that the work doesn’t end there.

Examples of Automated Tools (WAVE, axe)

WebAIM WAVE Toolbar

First, let’s look at WAVE. The benefit of this tool is that it visually displays errors where they occur, so you can quickly see them on the page. In addition to errors and warnings, it also shows structural elements present on the page and where ARIA is used.

A website page containing icons and short descriptions provided by the WebAIM Wave tool. Icons include errors and warnings, structural elements, and ARIA.
WebAim WAVE results at a glance.

The structure page is helpful for understanding how the page content is organized. This will impact how well AT users are able to navigate the page.

A visual outline of the page structure showing page regions and how they are nested.
Visual representation of the page structure.

The downside is that because it displays errors visually, it injects these elements into the markup. As a result, when you dig in a bit deeper, the code for the visual error icons will be sprinkled into the page code, so it becomes difficult to separate the two. You may have to go back and forth between running the page and refreshing it without all of the additional WAVE info, which can be time-consuming and confusing.

Also, the visual clutter sometimes makes things difficult to see, and some information, both WAVE and site content, can be cut off and hard to inspect.


Axe is a bit more on the technical side, and it doesn’t show you the structural features and where ARIA markup is used. Instead, it will present the errors in a list within your inspector tools. The benefit of axe is that you can easily switch back and forth between the list of errors and the code where the errors were found by clicking “inspect node.” For each issue, you can see a more detailed description and tips on fixing it, along with the corresponding code snippet. If there is more than one instance, you can click through each one.

aXe results shown within the inspector tools. Contains a summary or results, as well as details and instructions on how to fix one of the issues.
Axe analysis results.

Interpreting Results 

For all issues found by automated checkers, make sure to go through them manually before including them in your report. Often you’ll want to add details beyond what’s available within the checker results, like how it may impact the experience and screenshots of where the issue happens. It’s also an excellent way to validate errors you may encounter in your manual and AT testing.

WAVE Results

In the Details tab, you’ll see each individual issue, and you can also toggle different types of information to reduce visual clutter on the page.

Details tab showing categories of issues with specific types listed under each category. Both the categories and issue types can be toggled on or off.
WebAIM WAVE Details tab.

If you click on the information icon next to the issue, details about that error will appear in the Reference tab. The details description will explain why the error is essential, how to fix it, and a link to the related WCAG criterion.

Error details including why the error matters, how to fix it, the algorithm used for identifying the error, and related standards and guidelines.
Detailed error information in the Reference tab.

Axe Results

You can read a quick summary of the issue in the Issue Description section, or press the Learn More link for more details. It will redirect you to the Deque website page that provides detailed information about the problem. You can toggle the highlight option to see where the error appears on the page. Make a note of the issue tags at the bottom of the window. These will tell you which WCAG level and the related success criteria.

aXe issue description including a snippet of the error source code, and instructions of fixing the issue.
Axe issue description and instructions for solving it.

Exercise: Test Your Pages With an Automated Checker

Go to each of the pages you have selected when setting up your testing session. In Chrome, run each page through the WAVE tool, and axe plugin. Review the findings and summarize them in your report. Remember, not every error necessarily has to go into the report. You may come across false positives, so use your judgment.

Let’s Recap!

  • Automated testing tools are very limited. Interpreting the results will always require human judgment. 

  • WebAIM WAVE is a more visually-based tool. In addition to errors and warnings, it identifies structural elements features, and ARIA markup. 

  • Axe is more technical in how it presents errors and allows users to easily switch between the list of errors and the source code where they were observed to identify the context and provide further details. 

Ready to dive in deeper? Let’s look at some manual checks next. You’ll get a chance to inspect some code and look at the site content and interactions more closely. 

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