AChecker is an open source Web accessibility evaluation tool. It can be used to review the accessibility of Web pages based on a variety international accessibility guidelines. Use the Public AChecker to evaluate the accessibility of a Web site you know. Download AChecker to setup your own version.

Accessibility Guidelines Supported:

Why is AChecker Different than Other Accessibility Tools?

Automated accessibility checkers can only identify a limited number of barriers in Web content with certainty. A human must interact with an accessibility review to make decisions on potential problems automated tools can not identify. For example, any check that requires the evaluation of meaning, such as whether link text accurately describes the purpose of a link, or whether Alt text sufficiently describes the meaning contained in an image, a human must make a decision. If an accessibility checker is not asking the evaluator to make manual checks, it is not doing a thorough job.

Evaluating accessibility with AChecker is an interactive ongoing process. AChecker knows when it is unable to identify a potential problem and will ask the evaluator to manually check for the problem. Because Web content often changes, AChecker can be used to monitor the accessibility of Web content as it evolves. Linking the AChecker conformance seal from a completed evaluation into a Web page, indicates the site is serious about accessibility. Clicking on a seal retrieves the original evaluation from AChecker, or it runs the evaluation again if the content of the page has changed.

AChecker also allows users to create accessibility guidelines, if for instance they are working in an enclosed environment that requires a specific level of accessibility. It also allows users to create new checks for the system as technology develops and makes it possible to check issue that may not have previously been possible. It is also an open system, so those who want to develop expertise in accessibility evaluation have full access to all the inner workings of the system, all the accessibility checks and the solutions for fixing problems found by the system, and a full range of test files that verify exactly what each accessibility check is checking.

How to Use AChecker

AChecker HowTo
  Using AChecker to Test Web Accessibility (YouTube) (8:52)
AChecker HowTo
  AChecker Basics (Windows Media/Quicktime)
  1. Enter a URL to a Web page, upload an HTML file, or paste HTML from the clipboard.
  2. Review Known Problems and make the suggested corrections to the Web page, then run AChecker again. Known Problems are those that AChecker knows with certainty are accessibility barriers.
  3. Review Likely Problems. Likely Problems are those that AChecker has identified as probably barriers, but can not be sure. They require a human to make a decision. Login, then answer the questions to confirm if likely problems are actual problems, and make corrections to the Web Page where likely problems are confirmed. Save your decisions after all Likely Problems are resolved.
  4. Review all Potential Problems. Potential Problems are those that AChecker can not identify, that require a human to make a decision. Answer the questions to confirm if potential problems are actual problems, and make corrections to the Web page where potential problems are confirmed. Save your decisions after all Potential problems are resolved. When all Known, Likely, and Potential problems have been resolved, a Conformance Seal is issued.
  5. Paste Conformance Seal into Reviewed Web Page. Copy the HTML generated after completing an accessibility review into the HTML of the reviewed page. Run AChecker again on the Web page, which will recognize the addition of the seal as a change, and resolve the new Likely and Potential problems. You may copy the conformance seal to a local folder, and adjust the path to the image in the copied HTML.

AChecker Features

Regular Users

Registered Users



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This project is made possible in part by the Government of Ontario's Enabling Change Program.