Browser MCP Control

Skill by ara.so — MCP Skills collection.

What Browser MCP Does

Browser MCP is a Model Context Protocol server that bridges AI assistants to your local Chrome browser through a Chrome extension. Unlike headless automation tools, it operates on your existing browser profile, preserving login sessions and cookies, reducing CAPTCHA triggers and bot detection.

The architecture uses:

• MCP Server (stdio) that AI clients spawn as subprocess
• WebSocket bridge (port 9009) for extension communication
• Chrome Extension that executes commands in active tabs
• Optional Redis for session persistence

Installation

1. Install the MCP Server

git clone https://github.com/BrowserMCP/mcp.git
cd mcp
npm install
npm run build

2. Configure Your MCP Client

Add to your MCP settings (Cursor, Claude Desktop, VS Code, etc.):

Cursor/Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "browsermcp": {
      "command": "node",
      "args": ["/absolute/path/to/mcp/dist/index.js"]
    }
  }
}

VS Code (.vscode/settings.json):

{
  "mcp.servers": {
    "browsermcp": {
      "command": "node",
      "args": ["/absolute/path/to/mcp/dist/index.js"]
    }
  }
}

3. Install Chrome Extension

Install the Browser MCP extension from browsermcp.io or the Chrome Web Store.

4. Connect Extension

1. Restart your AI client to spawn the MCP server
2. Open Chrome and click the Browser MCP extension icon
3. Click Connect on the active tab
4. Extension connects via WebSocket to localhost:9009

Configuration

Create .env in the project root:

# WebSocket port for Chrome extension
WS_PORT=9009

# Logging
LOG_LEVEL=info

# Redis (optional session persistence)
REDIS_ENABLED=false
REDIS_HOST=127.0.0.1
REDIS_PORT=6379
REDIS_PASSWORD=
REDIS_DB=0
REDIS_KEY_PREFIX=browsermcp:
REDIS_SESSION_TTL_SECONDS=86400

Core Tools

Navigation Tools

browser_navigate

Navigate to a URL:

// Tool call from AI
{
  "tool": "browser_navigate",
  "arguments": {
    "url": "https://github.com/trending",
    "waitUntil": "networkidle"
  }
}

Parameters:

• url (required): Target URL
• waitUntil (optional): load, domcontentloaded, networkidle

browser_go_back / browser_go_forward

{
  "tool": "browser_go_back"
}

{
  "tool": "browser_go_forward"
}

browser_wait

Wait for page state or timeout:

{
  "tool": "browser_wait",
  "arguments": {
    "seconds": 3
  }
}

Interaction Tools

browser_click

Click an element by selector or coordinates:

// Click by CSS selector
{
  "tool": "browser_click",
  "arguments": {
    "selector": "button.submit-btn"
  }
}

// Click by coordinates
{
  "tool": "browser_click",
  "arguments": {
    "x": 250,
    "y": 400
  }
}

Parameters:

• selector (optional): CSS selector
• x, y (optional): Pixel coordinates
• button (optional): left, right, middle
• clickCount (optional): Single/double/triple click

browser_type

Type text into an input:

{
  "tool": "browser_type",
  "arguments": {
    "selector": "input[name='email']",
    "text": "user@example.com",
    "pressEnter": false
  }
}

Parameters:

• selector (required): CSS selector for input
• text (required): Text to type
• pressEnter (optional): Submit after typing

browser_select_option

Select dropdown option:

{
  "tool": "browser_select_option",
  "arguments": {
    "selector": "select#country",
    "value": "USA"
  }
}

browser_hover

Hover over element:

{
  "tool": "browser_hover",
  "arguments": {
    "selector": ".tooltip-trigger"
  }
}

browser_press_key

Press keyboard keys:

{
  "tool": "browser_press_key",
  "arguments": {
    "key": "Enter"
  }
}

Common keys: Enter, Escape, Tab, Backspace, ArrowDown, ArrowUp

Inspection Tools

browser_snapshot

Get ARIA accessibility tree as YAML:

{
  "tool": "browser_snapshot"
}

Returns structured page content for AI analysis:

- role: navigation
  name: Main navigation
  - role: link
    name: Home
  - role: link
    name: About
- role: main
  - role: heading
    name: Welcome
    level: 1
  - role: article
    - role: heading
      name: Getting Started
      level: 2

browser_screenshot

Capture page screenshot:

{
  "tool": "browser_screenshot",
  "arguments": {
    "quality": 90,
    "fullPage": false
  }
}

Parameters:

• quality (optional): JPEG quality 0-100
• fullPage (optional): Capture entire scrollable page

Returns base64-encoded image.

browser_get_console_logs

Retrieve browser console messages:

{
  "tool": "browser_get_console_logs"
}

Returns array of log entries with type, message, timestamp.

Common Patterns

Login Flow

// 1. Navigate to login page
await useTool("browser_navigate", {
  url: "https://app.example.com/login"
});

// 2. Fill credentials
await useTool("browser_type", {
  selector: "input[name='username']",
  text: process.env.USERNAME
});

await useTool("browser_type", {
  selector: "input[name='password']",
  text: process.env.PASSWORD
});

// 3. Submit
await useTool("browser_click", {
  selector: "button[type='submit']"
});

// 4. Wait for redirect
await useTool("browser_wait", {
  seconds: 2
});

Form Automation

// Navigate to form
await useTool("browser_navigate", {
  url: "https://example.com/contact"
});

// Fill text fields
await useTool("browser_type", {
  selector: "#name",
  text: "John Doe"
});

await useTool("browser_type", {
  selector: "#email",
  text: "john@example.com"
});

// Select dropdown
await useTool("browser_select_option", {
  selector: "#topic",
  value: "sales"
});

// Fill textarea
await useTool("browser_type", {
  selector: "textarea#message",
  text: "I'd like to discuss..."
});

// Submit
await useTool("browser_click", {
  selector: "button.submit"
});

Data Extraction

// Navigate to target page
await useTool("browser_navigate", {
  url: "https://news.ycombinator.com"
});

// Get structured content
const snapshot = await useTool("browser_snapshot");

// Parse YAML snapshot to extract:
// - Headlines (role: link)
// - Scores (role: text)
// - Comment counts

// Or take screenshot for visual verification
const screenshot = await useTool("browser_screenshot", {
  fullPage: true
});

Multi-Step Workflow

// 1. Search
await useTool("browser_navigate", {
  url: "https://github.com/search"
});

await useTool("browser_type", {
  selector: "input[name='q']",
  text: "mcp server",
  pressEnter: true
});

await useTool("browser_wait", { seconds: 2 });

// 2. Filter results
await useTool("browser_click", {
  selector: "button[data-filter='repositories']"
});

await useTool("browser_wait", { seconds: 1 });

// 3. Extract data
const content = await useTool("browser_snapshot");

// 4. Navigate to first result
await useTool("browser_click", {
  selector: ".repo-list-item:first-child a"
});

// 5. Capture repo details
const repoSnapshot = await useTool("browser_snapshot");

Error Handling

Connection Errors

try {
  await useTool("browser_navigate", {
    url: "https://example.com"
  });
} catch (error) {
  if (error.message.includes("No connection")) {
    console.error("Chrome extension not connected. Open extension popup and click Connect.");
  }
}

Timeout Handling

// Increase wait time for slow pages
await useTool("browser_navigate", {
  url: "https://slow-site.com",
  waitUntil: "networkidle"
});

await useTool("browser_wait", {
  seconds: 5
});

Element Not Found

// Wait before interaction
await useTool("browser_wait", { seconds: 2 });

await useTool("browser_click", {
  selector: ".dynamic-content button"
});

// Or use snapshot to verify element exists
const snapshot = await useTool("browser_snapshot");
// Parse to check for expected elements

Development & Testing

Run in Development Mode

npm run dev

Type Checking

npm run typecheck

Run Tests

npm test
npm run test:watch

Use MCP Inspector

Debug tools interactively:

npm run build
npm run inspector

Enable Debug Logging

LOG_LEVEL=debug node dist/index.js

Troubleshooting

Extension Not Connecting

Symptom: Tools fail with "No connection to browser extension"

Solutions:

1. Click Browser MCP extension icon in Chrome
2. Click Connect on the active tab
3. Verify WebSocket port 9009 is not blocked
4. Check extension is enabled in chrome://extensions

Port Already in Use

Symptom: Error: listen EADDRINUSE: address already in use :::9009

Solutions:

# Find process using port 9009
lsof -i :9009
kill -9 <PID>

# Or use different port
WS_PORT=9010 node dist/index.js

Update MCP config with new port.

Tools Timeout

Symptom: Operations timeout after 30 seconds

Solutions:

1. Ensure browser tab is active and visible
2. Check network connection for slow pages
3. Use browser_wait before interactions
4. Verify extension is connected (green indicator)

No Tools Available

Symptom: AI client doesn't show browser tools

Solutions:

1. Verify absolute path in MCP config
2. Restart AI client after config changes
3. Check npm run build completed successfully
4. Confirm Node.js 18+ installed

Redis Connection Failures

Symptom: Redis errors in logs (when enabled)

Solutions:

# Verify Redis running
redis-cli ping
# Expected: PONG

# Or disable Redis
REDIS_ENABLED=false

Server continues without persistence if Redis unavailable.

Architecture Notes

• Stdio Transport: Server communicates with AI client via stdin/stdout
• Stderr Logging: All diagnostics go to stderr to preserve MCP protocol
• Single Connection: Only one extension WebSocket connection active at a time
• Session Preservation: Uses existing Chrome profile, maintaining cookies and login state
• Type Safety: End-to-end TypeScript with Zod schema validation

Security Considerations

• Server runs locally on localhost only
• No data sent to remote servers
• Extension requires explicit user connection per tab
• Use environment variables for credentials, never hardcode
• Redis passwords should be set if exposing port

Use Cases

• Web Scraping: Extract data while authenticated
• Form Automation: Fill multi-page forms
• Testing: Verify UI workflows with real browser
• Research: Navigate sites requiring JavaScript
• Data Collection: Gather information from protected content
• Monitoring: Check site status and capture evidence