False positives and false assurance

When using automated 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.

False positives

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

Automated 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

Automated 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.

False assurance

Automated tools may also give a false sense of compliance, this is not only because the 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, the automated 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 any context to the page.

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

Follow the alt decision tree

Use the alt decision tree if you're unsure whether you need to use 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 accruately describes the image.

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

Don't

Use the filename or misleading descriptions.

alt="image123"

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Information about this page

• Created: 1 August 2024
• Last reviewed: 1 August 2024
• Last updated: 1 August 2024
• Reason this page exists: This page exists to help people understand how to use tools to test for, and understand accessibility issues in a product.
• Suggest a change or comment: Issue 37