The Transparency of Automatic Web Accessibility Evaluation Tools: Design Criteria, State of the Art, and User Perception

Several Web accessibility evaluation tools have been put forward to reduce the burden of identifying accessibility barriers for users, especially those with disabilities. One common issue in using accessibility evaluation tools in practice is that the results provided by different tools are sometimes unclear, and often diverging. Such limitations may confuse the users who may not understand the reasons behind them, and thus hamper the possible adoption of such tools. Hence, there is a need for tools that shed light on their actual functioning, and the success criteria and techniques supported. For this purpose, we must identify what criteria should be adopted in order for such tools to be transparent and to help users better interpret their results. In this paper, we discuss such issues, provide design criteria for obtaining user-centred and transparent accessibility evaluation tools, and analyse how they have been addressed by a representative set of open, license-free, accessibility tools. We also report on the results of a survey with 138 users of such tools, aimed at capturing the perceived usefulness of previously identified transparency requirements. Finally, we performed a user study with 18 users working in the Web design or accessibility fields with the goal of receiving more feedback about the transparency of a selected subset of accessibility tools.