Web Accessibility Testing MCP

A11y MCP is a Model Context Protocol (MCP) server designed to provide Large Language Models (LLMs) with direct access to web accessibility testing capabilities. It serves developers, designers, and content creators who need to integrate automated accessibility checks into their workflows, enabling LLMs to programmatically assess web content for compliance with accessibility standards. The primary purpose is to bridge the gap between AI assistants and web accessibility evaluation, allowing for conversational and automated testing.

Web accessibility is a critical requirement for inclusive digital experiences, ensuring that websites and applications are usable by people with disabilities. However, manual accessibility testing is time-consuming and requires specialized knowledge. Many development teams struggle to consistently identify and fix accessibility issues, leading to non-compliant websites that exclude users. This server addresses the problem by automating accessibility testing through LLMs, making it easier to integrate checks into development pipelines and content creation processes.

One key feature is the ability to test web pages at any public URL for accessibility issues with customizable viewport dimensions. Users can specify width and height parameters to simulate different devices, such as mobile viewports like iPhone 12/13 (390x844 pixels) or default desktop viewports (1280x800 pixels). This allows for responsive design testing across various screen sizes, ensuring accessibility compliance on all devices.

Another major capability is testing raw HTML strings for accessibility issues. This feature enables developers to analyze code snippets, components, or dynamic content without deploying to a live URL. It supports the same customizable viewport and WCAG tag filtering as URL testing, making it ideal for testing individual UI components, email templates, or content management system outputs during development.

The server provides comprehensive WCAG compliance testing against various standards including WCAG 2.0, 2.1, and 2.2 at different conformance levels (A, AA, AAA). Users can specify which accessibility tags to test against, allowing for targeted compliance checks. Common tags include wcag2a, wcag2aa, wcag2aaa, wcag21a, wcag21aa, wcag22aa, and best-practice guidelines for comprehensive coverage.

Additional specialized tools include color contrast analysis to check if foreground and background color combinations meet WCAG requirements, ARIA attribute validation to test proper usage of accessibility attributes in HTML, and orientation lock detection to identify content that forces specific screen orientations. The server also offers rule exploration capabilities, allowing users to get information about available accessibility rules with optional filtering by tags.