Excalidraw MCP Server

excalidraw-mcp-server

The only Excalidraw MCP server with security hardening, inline diagram rendering, and real-time canvas sync.

What it does

Ask your AI to draw a diagram, and it appears right inside the chat. The MCP server gives Claude Desktop, ChatGPT, VS Code, and Cursor a full set of drawing tools backed by the Excalidraw format -- with API authentication, rate limiting, and input validation on every operation.

v2.0 adds MCP Apps support: diagrams stream inline as interactive SVG widgets with draw-on animations, and you can export any diagram to excalidraw.com with one click.

Two modes, zero config

Standalone mode (default) -- just install and go. The server runs with an in-process element store. No canvas server, no API keys, no setup. Your MCP client calls the tools, and diagrams render inline.

Connected mode -- start the optional canvas server for real-time browser sync. Multiple clients can collaborate on the same canvas through authenticated WebSocket connections. File persistence keeps state across restarts.

The server auto-detects which mode to use: if a canvas server is reachable, it connects to it. Otherwise it falls back to standalone.

Architecture

Diagram created with excalidraw-mcp-server -- edit in Excalidraw

Features

MCP Apps (v2.0)

• Inline diagram rendering in Claude Desktop, ChatGPT, and VS Code
• Streaming SVG with draw-on animations as elements arrive
• Export to excalidraw.com with one click
• Element reference cheatsheet via read_me tool

16 MCP tools

• Create, update, delete, and query elements (rectangle, ellipse, diamond, arrow, text, line, freedraw)
• Batch create up to 100 elements at once
• Group, ungroup, align, distribute, lock, unlock
• Mermaid diagram conversion
• SVG and PNG export

Security

• API key authentication with constant-time comparison
• Origin-restricted CORS (no wildcards)
• WebSocket auth with token and origin validation
• Standard and strict rate limiting tiers
• Bounded Zod schemas with .strict() on every endpoint
• Helmet.js security headers with CSP

Infrastructure

• Real-time WebSocket sync across browser clients
• Optional atomic-write file persistence
• Structured pino audit logging

Install

npm install -g excalidraw-mcp-server

Or run directly:

npx excalidraw-mcp-server

Quick start

Standalone (recommended for most users)

Just point your MCP client at the server. No canvas server needed.

{
  "mcpServers": {
    "excalidraw": {
      "command": "npx",
      "args": ["excalidraw-mcp-server"]
    }
  }
}

Then ask your AI: "Draw an architecture diagram showing a load balancer, three app servers, and a database"

Connected mode (real-time browser sync)

# Generate an API key
node scripts/generate-api-key.cjs

# Start the canvas server
EXCALIDRAW_API_KEY=<your-key> npm run canvas

# Open http://localhost:3000 to see the live canvas

Point your MCP client at the server with the same API key:

{
  "mcpServers": {
    "excalidraw": {
      "command": "npx",
      "args": ["excalidraw-mcp-server"],
      "env": {
        "EXCALIDRAW_API_KEY": "<your-key>",
        "CANVAS_SERVER_URL": "http://127.0.0.1:3000"
      }
    }
  }
}

MCP tools