Excalidraw

excalidraw-mcp-server

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

[CI] [npm] [npm downloads] [License: MIT] [Node]

[Demo: architecture diagram being drawn element-by-element in real-time through WebSocket 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

[Architecture: MCP clients connect via stdio to the server, which operates in standalone mode with an in-process store and inline widget, or in connected mode with a canvas server, WebSocket browser frontend, and file persistence]

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 keynode scripts/generate-api-key.cjs
# Start the canvas serverEXCALIDRAW_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

Security comparison

Configuration

All settings via environment variables. Copy .env.example to .env and adjust as needed.

MCP client configuration

Claude Desktop

Add to claude_desktop_config.json:

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

Cursor

Add to .cursor/mcp.json in your project root:

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

VS Code

Add to your MCP settings:

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

For connected mode, add "env": { "EXCALIDRAW_API_KEY": "<key>", "CANVAS_SERVER_URL": "http://127.0.0.1:3000" } to the config above. Replace <key> with the key from node scripts/generate-api-key.cjs.

Development

# Install dependenciesnpm ci
# Run in development mode (watch + Vite dev server)npm run dev
# Run testsnpm test
# Run tests with coveragenpm run test:coverage
# Lintnpm run lint
# Type checknpm run type-check
# Build (server + widget + frontend)npm run build

Project structure

src/  mcp/              MCP server (stdio transport)    tools/          16 tool implementations    apps/           MCP Apps wiring, standalone store, cheatsheet    schemas/        Zod schemas and input limits    canvas-client.ts  HTTP client for canvas server    index.ts        MCP server entry point  canvas/           Canvas server (Express + WebSocket)    middleware/      Auth, CORS, rate limiting, audit, security headers    routes/         REST API routes + SVG export    ws/             WebSocket handler and protocol    store/          Element storage (memory + file)    index.ts        Canvas server entry point  shared/           Shared config, types, loggingwidget/             MCP Apps inline widget (Vite + singlefile build)frontend/           Excalidraw React frontend (browser)test/               Unit and integration tests (290 tests)

Migrating from v1.x

Zero-config upgrade. All 14 original tools work identically -- create_view and read_me are additive. The canvas server is now optional (standalone mode activates automatically).

npm install -g excalidraw-mcp-server@2

Existing MCP client configs (stdio transport, tool names) continue to work without changes.

License

MIT