Three.js DevTools MCP

threejs-devtools-mcp

MCP server for inspecting Three.js scenes in real time, trying changes live in the browser, and turning them into code. 69 tools cover objects, materials, shaders, textures, animation, performance and memory, plus website audits, video frame capture and Playwright helpers.

Zero changes to your project. Works with vanilla Three.js and React Three Fiber, on WebGLRenderer and WebGPURenderer.

Setup

1. Add the MCP server

claude mcp add threejs-devtools-mcp -- npx threejs-devtools-mcp

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

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

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

{
  "servers": {
    "threejs-devtools-mcp": {
      "command": "npx",
      "args": ["-y", "threejs-devtools-mcp"]
    }
  }
}

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "threejs-devtools-mcp": {
      "type": "local",
      "command": ["npx", "-y", "threejs-devtools-mcp"],
      "enabled": true
    }
  }
}

2. Start your dev server and open the browser

Start your Three.js dev server as usual (npm run dev). The MCP server auto-detects the port from package.json and opens a browser at localhost:9222 with the devtools bridge injected.

Keep the browser tab open. The MCP server talks to your scene through a WebSocket bridge. Close the tab = tools stop working.

3. Ask the AI about your scene

"show me the scene tree"
"why is my model invisible?"
"try the car in red"          ← live preview, nothing saved
"keep it"                     ← written into your code
"audit this site for mobile"
"record a 5-second clip at 60 fps"

Look now vs. change the code

Every tool is labelled, so you and the AI always know what touches your files:

Every live-preview change is recorded. pending_changes returns each one as before → after with ready-to-paste code (vanilla Three.js and React Three Fiber) and where to find it in your project. revert_changes undoes them in the browser.

For websites and videos

• web_audit: checks for a blurry canvas (pixel ratio, missing resize), battery drain (rendering while idle or off-screen), heavy textures (oversized, not KTX2), expensive shadows, wrong color space and too many draw calls. Each finding comes with the fix.
• capture_frames: records a frame sequence for promo clips and reels. Time is virtualised, so the output is perfectly smooth at 30/60 fps even if your scene renders slowly. You get the ffmpeg command for MP4/WebM.

Skills

Ready-made workflows show up as slash commands in Claude Code, Cursor and other clients: inspect-scene, try-look, apply-to-code, web-perf-audit, prepare-video, debug-invisible, playwright-setup.

Playwright & Puppeteer

Three ways to connect, same tools in all of them: your own browser (default), a Chrome launched by the server (HEADLESS / CDP_PORT, shareable with Playwright MCP), or your own tests:

import { attachDevtools, waitForScene, threeCall } from 'threejs-devtools-mcp/playwright';

await attachDevtools(context, { connect: false });
await page.goto('http://localhost:5173');
await waitForScene(page);
expect((await threeCall(page, 'object_details', { name: 'Car' })).visible).toBe(true);

See Browsers, Puppeteer & Playwright.

In-browser overlay

A built-in devtools panel with live performance stats, interactive scene graph, material editor, and 3D object preview. Activated automatically or via the toggle_overlay tool.

Tip: name your objects

Unnamed objects show as (unnamed) in the scene tree. Named objects are easier to find and modify:

// Three.js
mesh.name = "player";

// React Three Fiber
<mesh name="player" geometry={geometry} material={material} />

Documentation

• Tools reference — all 69 tools by mode, skills, parameters
• Browsers, Puppeteer & Playwright — connection modes, e2e tests, CI tips
• Advanced setup — animations, scene export, configuration, transports
• Cursor setup — step-by-step guide for Cursor
• Token-efficient workflow — best practices for saving context

License

MIT