Testing for different access needs
False positives and false assurance
- Last reviewed
- 13 August 2026
Learn how to check accessibility test results and identify issues that automated tools may miss.
[NEED TO ADD IMAGES AND CHECK WITH JAKE RE THE 30-40% STAT]
Accessibility testing tools can help you identify potential barriers, but they cannot understand every aspect of your content or how it works for people. You need to validate test results and carry out manual checks to identify false positives and avoid false assurance.
Understand false positives
A false positive is an issue flagged by an accessibility testing tool that is not actually an accessibility issue when you review it manually.
Accessibility testing tools cannot understand all the context of your content. For example, they may not be able to tell:
- whether the text in a link clearly describes its purpose
- whether an image needs alternative text
- whether an error message provides the right information
- whether a contrast issue applies to an exempt type of content, such as a logo
Contrast in images
Some accessibility testing tools may flag contrast issues for content that is exempt from the contrast requirements, such as logos and branding.
Logos may not always have sufficiently contrasting foreground and background colours, but they are not required to meet these criteria. This is a false positive.
You should review the result manually to check whether the content needs to meet the relevant contrast requirements.
Understand false assurance
Accessibility testing tools can also give a false sense of compliance. They cannot identify every accessibility issue, so a test can pass even when there is a barrier that needs to be addressed.
[QUERY WITH JAKE: What is the source for the statement that automated accessibility tools identify around 30% to 40% of issues? Is this figure still appropriate to use?]
Example: false assurance with alt text
Alt text should describe the purpose or meaning of an image where this information is important to understanding the content. When testing images for alt text, an automated tool may check whether an image has an alt attribute, but it cannot determine whether the description accurately reflects the image.
This can provide false assurance because an image with alt text may pass the automated check even when the alt text is not descriptive or meaningful.
For example, an image of a classroom with alt="car" or alt="image123" could pass a basic automated check because an alt attribute is present. However, the description does not provide meaningful information about the image.
Do
Ensure alt text accurately describes the image. alt="A teacher standing in front of a class of children who are sitting at desks." [add image]
Do not
Do not use the filename or misleading descriptions. alt="image123" [add image]
If you're unsure whether to use alt text
Use the alt text decision tree to check whether you need to provide alt text.
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="".
Check your test results
Do not rely on automated testing alone. Review flagged issues manually and carry out additional manual and specialist testing where appropriate.
Testing with people who have different access needs can also help you identify barriers that automated tools cannot detect.
See [Find and use tools] for guidance on the tools and techniques you can use to test for accessibility.