MCP Accessibility Scanner 🔍

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A powerful Model Context Protocol (MCP) server that provides automated web accessibility scanning and browser automation using Playwright and Axe-core. This server enables LLMs to perform WCAG compliance checks, interact with web pages, manage persistent browser sessions, and generate detailed accessibility reports with visual annotations.

Features

Accessibility Scanning

✅ Full WCAG 2.0/2.1/2.2 compliance checking (A, AA, AAA levels)
📄 Detailed JSON reports with remediation guidance
🎯 Support for specific violation categories (color contrast, ARIA, forms, keyboard navigation, etc.)

Browser Automation

🖱️ Click, hover, and drag elements using accessibility snapshots
⌨️ Type text and handle keyboard inputs
🔍 Capture page snapshots to discover all interactive elements
📸 Take screenshots and save PDFs
🎯 Support for both element-based and coordinate-based interactions

Advanced Features

📑 Tab management for multi-page workflows
🌐 Monitor console messages and network requests
⏱️ Wait for dynamic content to load
📁 Handle file uploads and browser dialogs
🔄 Navigate through browser history

Installation

You can install the package using any of these methods:

Using npm:

npm install -g mcp-accessibility-scanner

Installation with Docker

A pre-built image is available on Docker Hub. The image includes Chromium and is pre-configured for containerized use — no extra flags needed.

Pull from Docker Hub:

docker pull justasmonkev/mcp-accessibility-scanner

Claude Code

 claude mcp add mcp-accessibility-scanner -s user -- docker run -i --rm justasmonkev/mcp-accessibility-scanner

To persist screenshots and reports on your host, add a volume mount:

claude mcp add mcp-accessibility-scanner -s user \
  -- docker run -i --rm -v /tmp/mcp-output:/app/output justasmonkev/mcp-accessibility-scanner

Without the -v mount, output files only exist inside the container and are lost when it exits.

Docker Compose

docker compose up -d

The Compose configuration publishes the unauthenticated MCP HTTP transport on 127.0.0.1:8931 only. Do not expose this port to untrusted networks.

Build from source

docker build -t mcp-accessibility-scanner .

Docker smoke test

npm run test:docker

Installation in VS Code

Install the Accessibility Scanner in VS Code using the VS Code CLI:

For VS Code:

code --add-mcp '{"name":"accessibility-scanner","command":"npx","args":["mcp-accessibility-scanner"]}'

For VS Code Insiders:

code-insiders --add-mcp '{"name":"accessibility-scanner","command":"npx","args":["mcp-accessibility-scanner"]}'

CLI Modes

The scanner can run in two modes depending on how you use it.

MCP server (default, no subcommand)

When launched without a subcommand, the process starts an MCP server that communicates over stdio. This is the mode used by MCP clients such as Claude Desktop, VS Code, and Claude Code -- you should never need to run it by hand.

npx mcp-accessibility-scanner            # starts the MCP server (stdio)

All of the MCP client configuration examples in this README already use this default mode.

Interactive REPL (interactive subcommand)

For manual terminal use, the interactive subcommand starts a readline REPL where you can call any tool directly:

$ npx mcp-accessibility-scanner interactive
Interactive mode. Type "<tool-name> <json>" to call a tool. Ctrl+D to exit.
> browser_navigate {"url": "https://example.com"}
> scan_page {"violationsTag": ["wcag21aa"]}
> audit_keyboard {"maxTabs": 30}

Each line is <tool-name> <json-arguments>. Omit the JSON to pass {}. Global browser connection flags still apply here, for example npx mcp-accessibility-scanner --headless interactive. Use --mobile or PLAYWRIGHT_MCP_MOBILE=1 to emulate a generic mobile device (Pixel 10 for Chromium, iPhone 17 for WebKit). It cannot be combined with --device, CDP attach/launch modes, remote browser endpoints, or --extension.

Discovering available tools (list-tools subcommand)

To print every tool name and its description:

npx mcp-accessibility-scanner list-tools

Note: Tool names like browser_navigate and scan_page are MCP tool identifiers (and REPL commands in interactive mode). They are not shell subcommands -- you cannot run npx mcp-accessibility-scanner browser_navigate.

Configuration

Here's the Claude Desktop configuration:

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

Advanced Configuration

You can pass a configuration file to customize Playwright behavior:

{
  "mcpServers": {
    "accessibility-scanner": {
      "command": "npx",
      "args": ["-y", "mcp-accessibility-scanner", "--config", "/path/to/config.json"]
    }
  }
}

Configuration Options

Create a config.json file with the following options:

{
  "browser": {
    "browserName": "chromium",
    "launchOptions": {
      "headless": true,
      "channel": "chrome"
    },
    "cdpLaunch": {
      "command": "open",
      "args": ["-a", "Slack", "--args", "--remote-debugging-port={port}"],
      "startupTimeoutMs": 30000
    }
  },
  "timeouts": {
    "navigationTimeout": 60000,
    "defaultTimeout": 5000
  },
  "network": {
    "allowedOrigins": ["example.com", "trusted-site.com"],
    "blockedOrigins": ["ads.example.com"]
  }
}

Available Options:

• browser.browserName: Browser to use (chromium, firefox, webkit)
• browser.launchOptions.headless: Run browser in headless mode (default: true on Linux without display, false otherwise)
• browser.launchOptions.channel: Browser channel (chrome, chrome-beta, msedge, etc.)
• browser.cdpEndpoint: Attach to an already-running Chromium-family app with CDP enabled
• browser.cdpHeaders: Map of HTTP headers to send with the CDP connect request, e.g. { "Authorization": "Bearer <token>" }, for endpoints that require header-based authentication
• browser.cdpTimeout: Maximum time in milliseconds to wait when connecting to the CDP endpoint (default: 30000)
• browser.cdpLaunch: Launch a Chromium-family desktop app with CDP enabled, wait for the endpoint, and manage the child process lifecycle
• CDP attach modes preserve the target browser's existing default-context settings instead of applying Playwright's defaults.
• timeouts.navigationTimeout: Maximum time for page navigation in milliseconds (default: 60000)
• timeouts.defaultTimeout: Default timeout for Playwright operations in milliseconds (default: 5000)
• network.allowedOrigins: List of origins to allow (blocks all others if specified)
• network.blockedOrigins: List of origins to block

CLI equivalents are also available: --cdp-launch-command, --cdp-launch-args, --cdp-launch-cwd, --cdp-launch-port, --cdp-launch-startup-timeout, --cdp-endpoint, --cdp-header (repeat for multiple headers, e.g. --cdp-header "Authorization: Bearer <token>"), and --cdp-timeout. The CDP headers and timeout can also be set via the PLAYWRIGHT_MCP_CDP_HEADERS (one Name: Value entry per line) and PLAYWRIGHT_MCP_CDP_TIMEOUT environment variables.

HTTP Heartbeat

When the server runs with --port, it sends MCP heartbeat pings for Streamable HTTP sessions. Set PLAYWRIGHT_MCP_PING_TIMEOUT_MS to override the default 5000 ms timeout. Set it to 0 or any negative value to disable heartbeat pings for clients or proxies that do not answer server-initiated pings.

Available Tools

The MCP server provides comprehensive browser automation and accessibility scanning tools:

Core Accessibility Tool

scan_page

Performs a comprehensive accessibility scan on the current page using Axe-core.

Parameters:

• violationsTag: Array of WCAG/violation tags to check

Supported Violation Tags:

• WCAG standards: wcag2a, wcag2aa, wcag2aaa, wcag21a, wcag21aa, wcag21aaa, wcag22a, wcag22aa, wcag22aaa
• Section 508: section508
• Categories: cat.aria, cat.color, cat.forms, cat.keyboard, cat.language, cat.name-role-value, cat.parsing, cat.semantics, cat.sensory-and-visual-cues, cat.structure, cat.tables, cat.text-alternatives, cat.time-and-media

Audit Tools

audit_site

Crawls and scans multiple internal pages, then aggregates violations across the site.

• Default strategy: link-based BFS from the current URL
• Supports links, nav, sitemap, and provided URL strategies
• Always writes a JSON report (default filename: audit-site-{timestamp}.json)

Example flow:

1. Navigate to your site homepage with browser_navigate
2. Run audit_site with maxPages: 25 and maxDepth: 2
3. Review the report path returned by the tool (written to the MCP output directory)

scan_page_matrix

Runs Axe scans on the same page across viewport/media/zoom variants and compares deltas against baseline.

• Default variants: baseline, mobile, desktop, forced-colors, reduced-motion, zoom-200
• Supports custom variants and optional reload between variants
• Always writes a JSON report (default filename: scan-matrix-{timestamp}.json)

Example flow:

1. Navigate to a page state you want to validate
2. Run scan_page_matrix with defaults (or provide custom variants)
3. Review per-variant deltas and open the generated JSON report path

audit_keyboard

Audits real keyboard focus behavior by pressing Tab (and optional Shift+Tab) with practical heuristics.

• Checks skip links, focus visibility, focus jumps, and possible focus traps
• Optional issue screenshots (screenshotOnIssue)
• Always writes a JSON report (default filename: audit-keyboard-{timestamp}.json)

Example flow:

1. Navigate to the target page and let it fully load
2. Run audit_keyboard with maxTabs: 50
3. Review focus findings and open the generated JSON report path

Navigation Tools

browser_navigate

Navigate to a URL.

• Parameters: url (string)
• Non-2xx main-document responses are shown as an HTTP status line in page state.

browser_navigate_back

Go back to the previous page.

browser_navigation_timeout

Set default navigation timeout for existing tabs.

• Parameters: timeout (in ms; 30000-300000)

browser_default_timeout

Set default operation timeout for existing tabs.

• Parameters: timeout (in ms; 30000-300000)

Page Interaction Tools

browser_snapshot

Capture accessibility snapshot of the current page (better than screenshot for analysis). Large data: URL payloads in snapshot output are truncated to their media type prefix.

• Parameters: compress (optional boolean, default false)
  • When true, repeated non-interactive ARIA snapshot nodes are collapsed in the rendered response when a repeated structural pattern appears more than 100 times. The first 10 examples of each collapsed pattern are kept.
  • Use browser_evaluate() to retrieve the full uncompressed list when needed.

browser_find

Search the current page accessibility snapshot without returning the full snapshot.

• Parameters: text (case-insensitive substring) or regex (regular expression, supports /pattern/flags)
• Returns matching snapshot lines with surrounding context, shown under their path from the root of the tree; ... marks truncated off-path context.

browser_click

Perform click on a web page element.

• Parameters: element (description), ref (element reference), doubleClick (optional)

browser_type

Type text into editable element.

• Parameters: element, ref, text, submit (optional), slowly (optional)

browser_hover

Hover over element on page.

• Parameters: element, ref

browser_drag

Perform drag and drop between two elements.

• Parameters: startElement, startRef, endElement, endRef

browser_select_option

Select an option in a dropdown.

• Parameters: element, ref, values (array)

browser_fill_form

Fill multiple fields with one call.

• Parameters: fields (array of objects with name, type, ref, and value)

browser_press_key

Press a key on the keyboard.

• Parameters: key (e.g., 'ArrowLeft' or 'a')

browser_evaluate

Evaluate a JavaScript expression on the page, or on a specific element when a ref is provided. The function's return value is serialized back as the result.

• Parameters: function (e.g., () => document.title or (element) => element.textContent), element (optional), ref (optional)

Screenshot & Visual Tools

browser_take_screenshot

Take a screenshot of the current page.

• Parameters: filename (optional), type (png or jpeg), scale (css or device, default css), fullPage (optional), element/ref pair (for element screenshots)
• scale: device captures a high-resolution screenshot using device pixels (accounts for the device pixel ratio); scale: css keeps the image sized in CSS pixels.

browser_pdf_save

Save page as PDF.

• Parameters: filename (optional, defaults to page-{timestamp}.pdf)

This tool requires --caps pdf in the CLI.

browser_install

Install the configured browser engine (use when browser executable is missing).

• Parameters: none

Browser Management

browser_close

Close the page.

browser_resize

Resize the browser window.

• Parameters: width, height

Tab Management

browser_tabs

Manage browser tabs in one tool.

• Parameters: action (list, new, close, select) and optional index (for close and select).

Information & Monitoring Tools

browser_console_messages

Returns all console messages from the page. Large data: URL payloads in console messages are truncated to their media type prefix.

browser_network_requests

Returns all network requests since loading the page. Large data: URL payloads in request URLs are truncated to their media type prefix.

Utility Tools

browser_wait_for

Wait for text to appear/disappear or time to pass.

• Parameters: time (optional), text (optional), textGone (optional)

browser_handle_dialog

Handle browser dialogs (alerts, confirms, prompts).

• Parameters: accept (boolean), promptText (optional)

browser_file_upload

Upload files to the page.

• Parameters: paths (array of absolute file paths)

browser_verify_element_visible

Verify an element by ARIA role/name.

• Parameters: role, accessibleName

browser_verify_text_visible

Verify text visibility.

• Parameters: text

browser_verify_list_visible

Verify list items at a snapshot reference.

• Parameters: element, ref, items (array)

browser_verify_value

Verify an element value or checked state.

• Parameters: type, element, ref, value

These verification tools require --caps verify:

Vision Mode Tools (Coordinate-based Interaction)

These tools require --caps vision:

browser_mouse_move_xy

Move mouse to specific coordinates.

• Parameters: element, x, y

browser_mouse_click_xy

Click at specific coordinates.

• Parameters: element, x, y, button (optional: left/right/middle), clickCount (optional), delay (optional, ms between mouse down and up)

browser_mouse_drag_xy

Drag from one coordinate to another.

• Parameters: element, startX, startY, endX, endY

Note

Coordinate-based tools require element descriptions for permission checks, but the coordinates themselves are used for action targeting.

Usage Examples

Basic Accessibility Scan

1. Navigate to example.com using browser_navigate
2. Run scan_page with violationsTag: ["wcag21aa"]

Color Contrast Check

1. Use browser_navigate to go to example.com
2. Run scan_page with violationsTag: ["cat.color"]

Multi-step Workflow

1. Navigate to example.com with browser_navigate
2. Take a browser_snapshot to see available elements
3. Click the "Sign In" button using browser_click
4. Type "user@example.com" using browser_type
5. Run scan_page on the login page
6. Take a browser_take_screenshot to capture the final state

Page Analysis

1. Navigate to example.com
2. Use browser_snapshot to capture all interactive elements
3. Review console messages with browser_console_messages
4. Check network activity with browser_network_requests

Tab Management

1. Open a new tab with `browser_tabs` and `{"action":"new"}`
2. Navigate to different pages in each tab
3. Switch to a tab with `browser_tabs` and `{"action":"select", "index": 1}`
4. List all tabs with `browser_tabs` and `{"action":"list"}`

Waiting for Dynamic Content

1. Navigate to a page
2. Use browser_wait_for to wait for specific text to appear
3. Interact with the dynamically loaded content

Note: Most interaction tools require element references from browser_snapshot. Always capture a snapshot before attempting to interact with page elements.

Development

Clone and set up the project:

git clone https://github.com/JustasMonkev/mcp-accessibility-scanner.git
cd mcp-accessibility-scanner
npm install

License

MIT