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Open-source accessibility testing tools

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A Comparison of Open-Source Accessibility Testing Tools

(As at: December 2025)

Accessibility testing tools are programmes that can assist with testing the accessibility of websites and digital content. They help to automatically identify potential barriers on a website that may hinder people with visual, hearing, cognitive or motor impairments from using it. In this way, accessibility testing tools support developers, designers and organisations in creating accessible digital content. They help ensure compliance with guidelines for accessible web design, such as the Web Content Accessibility Guidelines (WCAG), as well as legal requirements.

However, accessibility testing tools cannot check all criteria for an accessibility test. Manual checking of content therefore remains necessary. For example, an accessibility testing tool can only detect whether an image has alternative text; the content of the alternative text must be checked manually.

There is a wide variety of different testing tools available. These tools are suitable for accessibility testing to varying degrees. In the following, various tools are presented and their key differences highlighted.

Testing tools

A basic distinction must be made between manual and automated testing tools.

Manual testing tools

Manual testing tools require additional human intervention to check the accessibility of a website. These tools are primarily used to support manual accessibility testing. Examples of manual accessibility testing tools include: screen readers, the keyboard (for checking whether a website can be used without a mouse) or a colour contrast checker.

Automated tools

Automated tools check websites independently and generate a report on any barriers present. These tools are usually used as browser extensions or via a programming interface (API) and can therefore be easily integrated into the development process.

Well-known automation tools include Axe, Wave and Siteimprove. These tools are offered free of charge by their developers as browser extensions. However, they are always closed-source applications – in other words, proprietary applications. This means that the source code is not publicly available.

question

This raises the question: Are there any efficient, free open-source alternatives?

Below, four open-source accessibility tools are examined in more detail:

The tools were assessed on the basis of the following criteria:

  • supported browsers
  • Ability to export the report (particularly to JSON)
  • Availability of WCAG references in the report
  • Clarity of error messages
  • Inclusion of recommendations for action
  • Other features

Results

AInspector is a Firefox add-on that assesses the accessibility of websites against the WCAG (WCAG 2.0, WCAG 2.1 or WCAG 2.2 Levels A and AA) and ARIA guidelines, using the OpenA11y Evaluation Library. The results are clearly organised by rule categories and WCAG guidelines.

Rating

  • Browser: Firefox (Download: https://addons.mozilla.org/en-US/firefox/addon/ainspector-wcag/)
  • Export: CSV, JSON
  • WCAG references: Are fully documented within the graphical user interface (GUI) and in the export
  • Error messages: brief, yet clear and detailed; in English only
  • Recommendations for action: Yes, with reference to the underlying criterion and its requirements. Based on this reference, a recommendation for action is provided to resolve the issue
  • Other: No registration required; no data collection; the validation rules and criteria against which the website is to be tested can be configured in the settings (WCAG 2.2, 2.1, 2.0; Level A and/or AA, ARIA 1.2 or 1.3)

Conclusion

AInspector is a comprehensive and user-friendly open-source tool for accessibility testing in the Firefox browser. It provides detailed reports, clear error messages and a complete reference to the WCAG criteria. It also offers customisation options that allow you to adjust the testing standards.

AInspector is therefore suitable for both technical and editorial checks. The only drawback is that AInspector is only available for Firefox and the error messages are in English only.

BAAT is an open-source script based on axe-core that can be used as a bookmarklet or a user script.

Rating

  • Browsers: Firefox, Chrome, Edge (Download: https://github.com/mindscreen/baat)
  • Export: JSON
  • WCAG references: Included in the export; available in the GUI only via a link to Deque University
  • Error messages: brief and clear; in English only
  • Recommendations for action: The error message and the report contain recommendations for resolving the issue. A link to Deque University (dequeuniversity.com) provides additional detailed guidance.
  • Other: No registration required; no data collection

Conclusion

BAAT is an open-source tool based on axe-core that can be used as a bookmarklet or user script in various browsers. It delivers reliable results and provides a solid foundation for automated accessibility checks.

Positive features include its ease of use, the ability to export reports in JSON format, and the link to Deque University, which offers further explanations and support. The error messages are concise but clearly worded.

Although BAAT’s GUI is straightforward, it does not display the underlying WCAG criteria directly. Furthermore, BAAT offers very few filtering and configuration options.

Overall, BAAT is a practical tool for quick accessibility checks.

QualWeb is a Chrome extension that checks websites against WCAG 2.1 guidelines and ACT rules.

Rating

  • Browser: Chrome (Download: https://chromewebstore.google.com/detail/qualweb-extension/ljgilomdnehokancdcbkmbndkkiggioc)
  • Export: JSON
  • WCAG references: These are referenced both in the report and in the GUI; in the GUI, however, only via the rule ID, which refers to the WCAG criteria
  • Error messages: Precise, with direct indication of the relevant line of code; in English only; filtering by warnings and ‘Failed’ criteria is possible
  • Recommendations for action: No, only an error description with a code reference
  • Other: No login required, no data collection; filtering by warnings and errors is possible

Conclusion

QualWeb provides precise technical analyses and highlights the relevant lines of code directly. This makes it easier to make corrections during the development process. However, the lack of recommendations for action and the presentation of WCAG criteria via Rule IDs make it difficult to interpret the results. Furthermore, the tool only checks against WCAG 2.1 and ACT rules, without taking ARIA or WCAG 2.2 into account. Overall, QualWeb is a useful tool for technical checks, but should be supplemented by other tools. It is suitable for developers during the ongoing development process.

Lighthouse is an open-source tool integrated into Chrome DevTools that assesses performance, SEO and best practices, as well as accessibility.

Rating

  • Browser: Chrome (Download: https://developer.chrome.com/docs/lighthouse?hl=de)
  • Export: No
  • WCAG references: Available, but very buried within links on the Deque University website
  • Error messages: Easy to understand, with references to Deque University’s documentation, which contains recommended actions with definitions, WCAG criteria and guidance
  • Recommendations for action: Yes, with additional documentation
  • Other: No installation or registration required; accessibility is rated on a scale of 0–100; separate accessibility analysis for desktop and mobile

Conclusion

Lighthouse is a tool integrated into Chrome that is suitable for quick accessibility checks. It provides clear error messages and links to the Deque University documentation.

However, some of the error messages contain only general indications (e.g. ‘contrast issue’ without any in-depth analysis) and the WCAG references can sometimes be confusing. It is also not possible to export the reports.

Overall, Lighthouse is suitable for an initial assessment of accessibility during the development process.

Overall assessment (qualitative)

Tool Browser Export WCAG References Recommendations Special features
AInspector Firefox JSON, CSV completely yes customizable testing criteria
BAAT Firefox, Chrome, Edge JSON in part via links yes uses axe-core
QualWeb Chrome JSON via rule-IDs no direct code line reference
Lighthouse Chrome no indirectly yes Part of Chrome DevTools

Conclusion

All the open-source accessibility testing tools examined assist in checking the accessibility of websites.

  • AInspector provides the most comprehensive and customisable results, but is limited to Firefox.
  • BAAT stands out for its browser independence and ease of integration, but offers a less user-friendly interface.
  • QualWeb delivers precise technical results, but is more suited to developers than to beginners.
  • Lighthouse, as an integrated tool, is ideal for quick initial checks, but is not sufficient for detailed audits.

Overall, the results show that open-source tools offer an alternative to proprietary applications – particularly for organisations that prioritise data protection, transparency and customisability.

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