A11yScope

a11yscope-mcp

WCAG 2.2 AA checks for AI coding agents. The same engine as the A11yScope Chrome extension, exposed as an MCP server so Claude Code, Cursor, Claude Desktop and other MCP clients can audit the pages they build and fix what they find.

Runs locally in headless Chrome. Nothing is uploaded, no account, no telemetry.

Install

Claude Code

claude mcp add a11yscope -- npx -y a11yscope-mcp

Cursor / Claude Desktop / any MCP client — add to the MCP config:

{  "mcpServers": {    "a11yscope": {      "command": "npx",      "args": ["-y", "a11yscope-mcp"]    }  }}

Needs Node 20 or newer and a Chromium-based browser. Installing downloads nothing: the first scan uses the Chrome, Chromium, Edge or Brave already on the machine, and only if none is found does it fetch a Chrome for Testing build (~150 MB, once) into Puppeteer's cache. To point it at a specific browser, set A11YSCOPE_CHROME to the executable path.

Tools

Options on both scan tools: include_review (items that need a human decision), include_passed, max_findings_per_rule, viewport size. scan_page also takes wait_ms for pages that render late.

Typical prompt: "Scan http://localhost:3000 with a11yscope and fix every violation, then scan again."

What it checks

Text alternatives (images, form labels, buttons, links, frames, SVG), colour contrast with the large-text and bold exemptions applied and translucent backgrounds composited, document structure (language, title, headings, main landmark, skip link, tables, lists, duplicate ids), and keyboard, pointer and ARIA (zoom lock, positive tabindex, aria-hidden focusable, nested interactive controls, 24×24 target size, autoplay, captions, invalid roles, required ARIA states, autocomplete, focus visibility).

Calibrated against sites built by accessibility practitioners: gov.uk, webaim.org, deque.com, a11yproject.com and w3.org/WAI all report zero violations. Anything reported there is treated as our bug until proven otherwise, and false-positive reports are the most useful thing you can send.

What it does not do

Automated checks find roughly a third of accessibility barriers. A clean result is a good sign, not a conformance claim. Whether alt text is accurate, whether a page makes sense in a screen reader, whether a keyboard user can finish a task — no tool can answer those, and this one does not pretend to. Anything it cannot decide comes back as review, not as pass or fail. It is not a substitute for an expert evaluation and does not certify compliance with the EAA, ADA, KWCAG or any other standard.

Licence

Copyright © 2026 Perceivable. Free to install and run, including commercially, through npm and MCP clients. The engine source is published so that "nothing leaves your machine" can be verified rather than trusted; it is not open source, and no licence is granted to copy, modify or redistribute it or to publish derivative works. Full terms: the LICENSE file in this package and at the repository root. Problems and false positives: https://github.com/perceivable/a11yscope/issues.