Multi-Browser Compatibility Evaluation of a CDN-Based Accessibility Plugin Following the WCAG 2.1 Standard

Website accessibility remains a barrier for users with visual and motor impairments, while modern sites keep adding interactive visual elements. This study develops a modular JavaScript accessibility plugin distributed through a Content Delivery Network, so that it can be attached to a site without altering the existing page structure. The plugin follows WCAG 2.1 and provides text-to-speech, voice command, display and text settings, magnifier, and keyboard navigation through a single control panel. A company profile website was used as the case study. Evaluation combined manual inspection using DevTools and a WCAG checklist with automated measurement using Lighthouse and DevTools Performance, followed by compatibility testing on Chrome, Firefox, Edge, and Brave. All features behaved as designed without JavaScript errors, and the performance score remained stable after activation, although features that change text spacing and page scale added rendering work. Display, text, and keyboard features ran consistently across the four browsers, whereas voice command failed on Firefox and Brave and behaved unstably on Edge because of differing speech recognition support. The results suggest that browser API dependency is the main limitation of overlay-based accessibility solutions. Findings are bounded by a single site, single run measurements, two rendering engines, and the absence of usability testing with users who have impairments.