A11y

Web Accessibility-Testing MCP Server enables large language models to query web accessibility testing APIs. It leverages the Deque axe-core suite and Puppeteer to assess web content for WCAG compliance, identify accessibility issues, and explore rules across WCAG versions.

How to use

You connect an MCP client to the a11y MCP server to run accessibility checks against web pages or HTML snippets. You can target specific WCAG standards, explore available rules, verify color contrast, validate ARIA usage, and detect orientation locks. Use the client to request tests for a URL or for an HTML string, then review the structured results that report violations, passes, and test metadata.

Common usage patterns include testing a live page or a plain HTML snippet, selecting the WCAG tags you want to test against, and inspecting the returned violations to guide fixes. You can also retrieve rule information to understand which checks exist and which rules you can enable for your tests.

How to install

Prerequisites: ensure you have a supported runtime for MCP servers, such as Node.js with npm installed.

Install and run the MCP server using the following runtime command. This runs the server as an independent process via npx and does not require a separate build step in this setup.

npx -y a11y-mcp-server

Configuration for client integration

If you are using a client that requires an MCP configuration file, you can enable the stdio-based server entry shown here. This configuration assumes you run the server via a local process started with npx.

{
  "mcpServers": {
    "a11y_mcp": {
      "command": "npx",
      "args": [
        "-y",
        "a11y-mcp-server"
      ]
    }
  }
}

Install notes for macOS, Windows, and Linux clients

Configure your client according to your platform so it can start and connect to the MCP server. The following platform-specific paths show where you place the MCP settings.

// macOS
'~/Library/Application Support/Claude/claude_desktop_config.json'

{
  "mcpServers": {
    "a11y-accessibility": {
      "command": "npx",
      "args": [
        "-y",
        "a11y-mcp-server"
      ]
    }
  }
}

// Windows
%APPDATA%\Claude\settings\claude_mcp_settings.json

{
  "mcpServers": {
    "a11y-accessibility": {
      "command": "npx",
      "args": [
        "-y",
        "a11y-mcp-server"
      ]
    }
  }
}

// Linux
~/.config/Claude/settings/claude_mcp_settings.json

{
  "mcpServers": {
    "a11y-accessibility": {
      "command": "npx",
      "args": [
        "-y",
        "a11y-mcp-server"
      ]
    }
  }
}

Notes

The server provides endpoints to test URLs and HTML strings, check WCAG compliance across versions 2.0, 2.1, and 2.2, explore available rules, analyze color contrasts, validate ARIA usage, and detect orientation locks. Expect a structured JSON response detailing violations, passes, and environment metadata.

Available tools

test_accessibility

Tests a URL for accessibility issues by analyzing the live page and applying WCAG tags as specified.

test_html_string

Tests an HTML string for accessibility issues, validating ARIA usage, semantic structure, and WCAG conformance.

get_rules

Retrieves information about available accessibility rules with optional filtering to help you plan tests.

check_color_contrast

Evaluates foreground and background color combinations against WCAG contrast requirements to ensure readability.

check_orientation_lock

Detects content that enforces a specific screen orientation, helping ensure responsive behavior.