Tools and testing

False positives

Guidance on how to deal with false positives and false assurances

When using accessibility testing tools, it's important to validate the results to avoid identifying false positives and ensure that no issues have been missed, thereby preventing false assurances.

Understand false positives

False positives are issues that are flagged by testing tools, but are not actually issues when reviewed manually.

Accessibility tools do not understand context, for example:

• they will not understand the content of an image
• the words in a link being descriptive or generic
• the content and context of an error message

Contrast in images

Checks may raise issues related to contrast minimum even for content that is exempt, such as logos and branding.

Logos, which might not always have sufficiently contrasting foreground and background colours are not required to meet these criteria. Therefore, this is considered a false positive.

Understand false assurance

Accessibility testing tools can also give a false sense of compliance, this is not only because tools only identify around 30% to 40% of issues, but also because of how the tools scan code to decide if accessibility issues are present.

For example

When scanning images for alt text, testing tools are looking for a yes, or no answer, to whether the image has alt text or not.

This can provide false assurance because if an image contains alt text it would pass this test, but the alt text may not be descriptive.

There is an exception to when alt text can be omitted, such as when an image is purely decorative and does not add context to the page.

In this case, add an empty alt tag, as follows alt="".

If you're unsure whether to use alt text

Use an alt decision tree to check if you need to use alt text.

Example of false assurance using alt text

If an image of a classroom had an alt tag of alt=”car” or alt=”image123”, this would still pass the automated test, whereas it should fail because of the lack of context that this provides to users.

Do

Ensure alt text accurately describes the image.

alt="A teacher standing in front of a class of children who are sitting at desks."

Don't

Do not use the filename or misleading descriptions.

alt="image123"