Access to the internet is essential to any individual, including people with disabilities that encounter many challenges and obstacles while browsing the Web. To tackle those problems, the Web Accessibility Initiative (WAI) [1], since its creation in 1997, has worked on improving accessibility of the Web for people with disabilities by providing guidelines (WCAG) and tools for Web Accessibility Assessments. This study aims to compare free and open-source tools from the official (W3C) list of WAETs for evaluating websites against the Web Content Accessibility Guidelines (WCAG) 2.1 standards [2]; the comparison is based on the coverage error ratio (CER) metric that compares the performance of WAETs in identifying Web accessibility problems.