Accessibility tools and testing
Understand accessibility test results
- Last reviewed
- 7 September 2026
- Owner
- DesignOps
Learn how to check accessibility test results, identify false positives and avoid false assurance.
Accessibility 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 a result flagged by an accessibility tool that is not actually an accessibility problem when you review it manually.
Accessibility tools cannot understand all the context of your content. For example, they may not understand:
- the purpose of link text
- whether an image needs alternative text
- the information an error message needs to provide
- whether a contrast issue applies to exempt content, such as a logo
Example: false positive contrast in images
Some accessibility tools may flag issues related to the WCAG (Web Content Accessibility Guidelines) contrast criterion for exempt content, such as logos and branding.
Logos may not always have sufficiently contrasting foreground and background colours, but they are not required to meet these contrast requirements. This is a false positive.
Review the result manually to check if the content needs to meet the relevant contrast requirements.
Understand false assurance
Accessibility tools can also give a false sense of compliance. They cannot identify every barrier, so an automated test can pass even when your product or service is not fully accessible.
Accessibility tools typically identify around 30% to 40% of accessibility issues. This means a service can pass automated testing while still having accessibility barriers.
Example: false assurance with alt text
Alt text should describe the purpose or meaning of an image when this information helps users understand the content.
When checking images for alt text, testing tools can determine whether an alt attribute is present, but they cannot determine whether the description accurately reflects the image. This can give false assurance: an image may pass an automated check even when its alt text is misleading or provides little useful information.
For example
For the image below:
alt="A teacher standing in front of a class of children who are sitting at desks."is useful as it describes the imagealt="image123"is not useful as it does not describe the image - do not use filenames or misleading descriptions
Both would pass a basic automated check. Review images in context to check that their alt text provides the information users need.
If you're unsure whether to use alt text
Use the alt decision tree to check whether you need to provide alt text.
You do not need to add alt text when an image is purely decorative and does not add context to the page. In this case, use an empty alt attribute: alt="".
Check your test results
Do not rely on automated testing alone. Review flagged results manually and carry out additional manual or specialist testing where appropriate.
Testing with people who have different access needs can also help you identify barriers that automated tools cannot detect.
Learn more about accessibility tools to help you identify barriers and test your products and services.