Validatehtml

validatehtml

Validate HTML, CSS, JSON, XML and accessibility from your terminal or your AI coding agent. Errors are spec violations, warnings are best practices, and modern valid code stays clean.

npx validatehtml index.html
npx validatehtml https://example.com
npx validatehtml http://localhost:3000 --type accessibility

No account and no key. Exit code 0 when it passes, 1 when it fails, 2 when it could not run, so it fits in a script or a build.

For AI coding agents (MCP)

Claude Code:

claude mcp add validatehtml -- npx -y validatehtml mcp

Cursor, Windsurf, VS Code and any other MCP client:

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

---

View the full README on GitHub