🚀 CanIUse MCP Server - Browser Compatibility Intelligence

A powerful Model Context Protocol (MCP) server that provides intelligent CSS/JS feature compatibility checking with configurable browser targets, polyfill support, and smart project scanning. Perfect for web developers using AI-powered tools like Cursor, Claude, and other MCP-compatible clients.

✨ Key Features

• 🔍 Smart Project Scanning: Automatically detect CSS/JS features in your codebase
• 🎯 Configurable Browser Targets: Support for any browser version with custom baselines
• 💊 Polyfill-Aware Checking: Mark features as "supported" when you have polyfills available
• ⚡ Batch Compatibility Analysis: Check entire projects across multiple browsers instantly
• 🛠️ Actionable Remediation: Get specific npm install commands, code examples, and configs
• 📋 Complete Toolchain Generation: Auto-generate Babel, PostCSS, Webpack, and CI configurations
• 🔧 Runtime Configuration: Configure via files, environment variables, or MCP commands

📦 Installation

Global Installation (Recommended)

npm install -g caniuse-mcp-server

Local Installation

npm install caniuse-mcp-server

🔌 Setup for MCP Clients

Option 1: Global Installation (Recommended)

First, install the package globally:

npm install -g caniuse-mcp-server

Cursor IDE

Add to your Cursor settings (Cmd/Ctrl + , → MCP):

{
  "mcpServers": {
    "caniuse": {
      "command": "caniuse-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "caniuse": {
      "command": "caniuse-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

Option 2: Using npx (Alternative)

If global installation doesn't work, use npx:

Cursor IDE

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

Claude Desktop

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

Option 3: Direct Node.js Path

If you have issues with command resolution:

Find your global npm bin path:

npm config get prefix
# On macOS/Linux, usually: /usr/local/bin or ~/.npm-global/bin
# On Windows: C:\Users\[username]\AppData\Roaming\npm

Use full path in MCP configuration:

{
  "mcpServers": {
    "caniuse": {
      "command": "/usr/local/bin/caniuse-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

⚡ Quick Start

1. Basic Compatibility Check

// Check your project against default baseline (Chrome 37)
scan_project

2. Configure Your Target Browser

// Set up for Chrome 57 with CSS Variables polyfill
manage_config {
  "action": "set_baseline",
  "baseline": "chrome-57"
}

manage_config {
  "action": "add_polyfill", 
  "polyfill": "css-variables"
}

3. Check Specific Features

// Check if features work in your target browsers
check_compatibility {
  "features": ["css-variables", "promise-allsettled"],
  "targets": ["chrome-57", "firefox-70"]
}

4. Get Fix Recommendations

// Get actionable remediation steps
get_fixes {
  "features": ["css-grid", "arrow-functions"],
  "includeCommands": true,
  "includeExamples": true
}

🛠️ Available Tools

Core Tools

scan_project - Smart Project Analysis

Automatically scans your project and detects compatibility issues.

// Basic project scan
scan_project

// Advanced scanning with custom targets
scan_project {
  "projectPath": "./src",
  "targets": ["chrome-57", "firefox-esr", "safari-12"],
  "maxDepth": 3,
  "excludeDirs": ["node_modules", "dist"]
}

check_compatibility - Feature Testing

Check specific features or files against browser targets.

// Test specific features
check_compatibility {
  "features": ["css-variables", "promise-allsettled"],
  "targets": ["chrome-57", "firefox-70"]
}

// Analyze specific files
check_compatibility {
  "files": ["src/styles/main.css", "src/utils/async.js"],
  "targets": ["chrome-57"]
}

get_fixes - Get Solutions

Receive actionable remediation steps and polyfill recommendations.

get_fixes {
  "features": ["css-variables", "promise-allsettled"],
  "priority": "critical",
  "includeExamples": true,
  "includeCommands": true
}

generate_configs - Build Tool Setup

Generate complete build configurations for your toolchain.

generate_configs {
  "configType": "all",
  "target": "chrome-57",
  "includePolyfills": true,
  "projectType": "react"
}

manage_config - Configuration Management

Configure baselines, polyfills, and browser targets.

// View current configuration
manage_config { "action": "view" }

// Set baseline browser
manage_config { 
  "action": "set_baseline", 
  "baseline": "chrome-57" 
}

// Add polyfill support
manage_config { 
  "action": "add_polyfill", 
  "polyfill": "css-variables" 
}

// Add custom browser target
manage_config {
  "action": "add_target",
  "targetName": "chrome-65",
  "browser": "chrome",
  "version": "65"
}

🎯 Browser Targets Supported

| Target | Browser | Version | Use Case | |--------|---------|---------|----------| | chrome-37 | Chrome | 37 | Legacy Android support | | chrome-latest | Chrome | Latest | Modern development | | firefox-esr | Firefox | 78 ESR | Enterprise compatibility | | safari-12 | Safari | 12 | iOS 12+ support | | ie-11 | Internet Explorer | 11 | Legacy Windows support | | edge-legacy | Edge | 18 | Pre-Chromium Edge |

🔧 Configuration

Configuration File (.caniuse-config.json)

Create a .caniuse-config.json in your project root to customize behavior:

{
  "defaultBaseline": "chrome-57",
  "customTargets": {
    "chrome-57": { "browser": "chrome", "version": "57" },
    "chrome-65": { "browser": "chrome", "version": "65" }
  },
  "polyfills": [
    "css-variables", 
    "promise-allsettled"
  ],
  "overrides": {
    "css-variables": "supported",
    "promise-allsettled": "supported"
  }
}

Quick Configuration Setup

// Create a configuration template
manage_config { "action": "create_template" }

// Or use pre-built examples

Copy example configurations from the examples/ directory:

# CSS Variables support for older browsers
cp node_modules/caniuse-mcp-server/examples/css-variables-polyfill.json .caniuse-config.json

# Promise.allSettled polyfill configuration  
cp node_modules/caniuse-mcp-server/examples/promise-allsettled-polyfill.json .caniuse-config.json

# Enterprise multi-browser support
cp node_modules/caniuse-mcp-server/examples/enterprise-config.json .caniuse-config.json

Environment Variables

Configure via environment variables for CI/CD:

# Set default baseline
export CANIUSE_DEFAULT_BASELINE="chrome-57"

# Configure polyfills
export CANIUSE_POLYFILLS='["css-variables","promise-allsettled"]'

# Set feature overrides
export CANIUSE_OVERRIDES='{"css-variables":"supported","promise-allsettled":"supported"}'

💡 Real-World Use Cases

1. CSS Variables Polyfill Support

// Set up CSS Variables for older browsers
manage_config {
  "action": "add_polyfill",
  "polyfill": "css-variables" 
}

manage_config {
  "action": "set_override",
  "feature": "css-variables",
  "override": "supported"
}

// Now CSS Variables will be treated as supported
check_compatibility {
  "features": ["css-variables"],
  "targets": ["chrome-40", "ie-11"]
}

2. Promise.allSettled Polyfill Support

// Configure Promise.allSettled polyfill
manage_config {
  "action": "add_polyfill",
  "polyfill": "promise-allsettled"
}

// Set baseline to older Chrome that needs polyfill
manage_config {
  "action": "set_baseline", 
  "baseline": "chrome-60"
}

// Check compatibility - will show as supported due to polyfill
check_compatibility {
  "features": ["promise-allsettled"],
  "targets": ["chrome-60", "firefox-70"]
}

// Get implementation guidance
get_fixes {
  "features": ["promise-allsettled"],
  "includeCommands": true,
  "includeExamples": true
}

3. Enterprise Legacy Browser Support

// Scan for enterprise browser compatibility
scan_project {
  "targets": ["chrome-50", "firefox-esr", "safari-12", "ie-11"]
}

// Configure extensive polyfill support
manage_config { "action": "create_template" }
// Edit .caniuse-config.json to include:
// "polyfills": ["css-variables", "promise-allsettled", "fetch", "object-assign"]

4. Modern Development with Progressive Enhancement

// Check latest browser features
check_compatibility {
  "features": ["css-container-queries", "css-cascade-layers"],
  "targets": ["chrome-latest", "firefox-latest", "safari-latest"]
}

// Get fallback strategies
get_fixes {
  "features": ["css-container-queries"],
  "includeExamples": true
}

📈 Enhanced Output Examples

Scan Project Output

{
  "status": "completed",
  "project": {
    "path": "./src",
    "scanned": "24 files",
    "jsFiles": 12,
    "cssFiles": 8,
    "featuresDetected": 15
  },
  "compatibility": {
    "targets": ["chrome-37"],
    "overallScore": 73,
    "criticalIssues": 3,
    "commonUnsupported": ["css-grid", "arrow-functions", "const"]
  },
  "recommendations": [
    {
      "type": "critical",
      "title": "Critical Features Unsupported",
      "message": "These essential features are unsupported: css-grid, arrow-functions",
      "action": "Implement polyfills or use alternative approaches immediately"
    }
  ],
  "nextSteps": [
    {
      "step": 1,
      "title": "Get specific fixes",
      "command": "Use get_fixes tool with features: css-grid, arrow-functions, const",
      "priority": "high"
    }
  ]
}

Get Fixes Output

{
  "features": ["css-grid"],
  "fixes": [
    {
      "feature": "css-grid",
      "priority": "critical",
      "alternatives": ["flexbox", "CSS tables", "float layouts"],
      "polyfills": ["CSS Grid Polyfill"],
      "commands": [
        {
          "type": "install",
          "description": "Install css-grid polyfills",
          "command": "npm install postcss-grid-kiss --save-dev"
        }
      ],
      "cssExample": "/* Instead of Grid */\n.container { display: grid; }\n\n/* Use Flexbox */\n.container { display: flex; }"
    }
  ],
  "quickStart": [
    {
      "step": 1,
      "title": "Install critical polyfills",
      "command": "npm install css-grid-polyfill --save",
      "priority": "critical"
    }
  ]
}

🔧 Configuration Examples

Babel Configuration (.babelrc)

{
  "presets": [
    ["@babel/preset-env", {
      "targets": { "chrome": "37" },
      "useBuiltIns": "usage",
      "corejs": 3
    }],
    "@babel/preset-react"
  ]
}

PostCSS Configuration

module.exports = {
  plugins: {
    'autoprefixer': {
      overrideBrowserslist: ['Chrome >= 37']
    },
    'postcss-custom-properties': {
      preserve: false
    }
  }
};

🏗️ Development Workflow Integration

Git Hooks

# .husky/pre-commit
echo "🔍 Checking browser compatibility..."
npx caniuse-mcp-server scan_project

CI/CD Pipeline

# .github/workflows/compatibility.yml
- name: Check Browser Compatibility
  run: |
    npm install -g caniuse-mcp-server
    caniuse-mcp-server scan_project
    caniuse-mcp-server get_fixes --features="css-grid,promise-allsettled"

🚨 Troubleshooting

Common Issues

"No tools found" Error in Cursor/Claude

This is the most common issue. Try these solutions in order:

1. Verify Global Installation

# Check if package is installed globally
npm list -g caniuse-mcp-server

# If not installed, install globally
npm install -g caniuse-mcp-server

# Test the command directly
caniuse-mcp-server
# Should show: "🚀 Enhanced CanIUse MCP Server running on stdio"

2. Check Your PATH

# Verify npm global bin is in your PATH
echo $PATH | grep $(npm config get prefix)/bin

# If not found, add to your shell profile (~/.bashrc, ~/.zshrc, etc.)
export PATH="$(npm config get prefix)/bin:$PATH"

# Then restart your terminal and MCP client

3. Try Different Installation Methods

# Method 1: Clean reinstall
npm uninstall -g caniuse-mcp-server
npm install -g caniuse-mcp-server

# Method 2: Install without global flag and use npx
npm install caniuse-mcp-server
# Then use "npx caniuse-mcp-server" in MCP config

# Method 3: Install via different package manager
# Using yarn
yarn global add caniuse-mcp-server

# Using pnpm
pnpm add -g caniuse-mcp-server

4. Update MCP Configuration Format Make sure your Cursor/Claude configuration uses the correct format:

❌ Incorrect:

{
  "mcpServers": {
    "caniuse": {
      "command": "caniuse-mcp-server"
    }
  }
}

✅ Correct:

{
  "mcpServers": {
    "caniuse": {
      "command": "caniuse-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

5. Test MCP Server Manually

# Test if the server responds to MCP protocol
echo '{"jsonrpc": "2.0", "id": 1, "method": "tools/list"}' | caniuse-mcp-server

# Should return a JSON response with available tools

Other Common Issues

"Module not found" errors

# Make sure package is installed correctly
npm install -g caniuse-mcp-server

# Clear npm cache if needed
npm cache clean --force

# Or use npx for one-time execution
npx caniuse-mcp-server

Configuration not loading

# Check if config file exists and is valid JSON
cat .caniuse-config.json | jq '.'

# Reset to defaults if corrupted
manage_config { "action": "reset" }

Polyfills not working

// Verify polyfill is added
manage_config { "action": "view" }

// Check override is set
manage_config {
  "action": "set_override",
  "feature": "css-variables",
  "override": "supported"
}

Permission errors on macOS/Linux

# Fix npm permissions
sudo chown -R $(whoami) $(npm config get prefix)/{lib/node_modules,bin,share}

# Or reinstall npm with a node version manager
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash
nvm install node

Platform-Specific Issues

macOS

# If using Homebrew node
brew reinstall node

# Check npm prefix
npm config set prefix ~/.npm-global
export PATH=~/.npm-global/bin:$PATH

Windows

# Run as Administrator and install globally
npm install -g caniuse-mcp-server

# Add npm global path to system PATH
# Usually: C:\Users\[username]\AppData\Roaming\npm

Linux

# Use node version manager to avoid permission issues
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
sudo apt-get install -y nodejs

Debug Mode

Enable verbose logging with environment variables:

export DEBUG="caniuse-mcp-server*"
caniuse-mcp-server

Still Having Issues?

1. Check Node.js version: Requires Node.js 18+

   node --version

2. Verify npm configuration:

   npm config list
   npm doctor

3. Try a clean environment:

   # Create a test directory
   mkdir test-caniuse && cd test-caniuse
   npx caniuse-mcp-server

4. Report the issue: If none of the above work, please open an issue at https://github.com/Amirmahdi-Kaheh/caniuse-mcp/issues with:

   • Your operating system
   • Node.js version (node --version)
   • npm version (npm --version)
   • Complete error message
   • MCP client you're using (Cursor, Claude Desktop, etc.)

🔗 Links & Resources

• NPM Package: https://www.npmjs.com/package/caniuse-mcp-server
• Can I Use Database: https://caniuse.com
• Model Context Protocol: https://docs.anthropic.com/en/docs/build-with-claude/mcp
• Cursor IDE: https://cursor.sh
• Claude Desktop: https://claude.ai/desktop

🤝 Contributing

We welcome contributions! Please see our contributing guidelines:

1. Report Issues: Found a bug or missing feature? Open an issue
2. Feature Requests: Have ideas for new functionality? Let us know
3. Pull Requests: Want to contribute code? Fork and submit a PR
4. Documentation: Help improve our docs and examples

Development Setup

git clone <your-fork-url>
cd caniuse-mcp-server
npm install
npm run dev  # Start in development mode

📊 Why Use CanIUse MCP?

Before

• Manual caniuse.com lookups
• Guessing at polyfill needs
• Trial-and-error browser testing
• Separate compatibility checking tools

After

• AI-powered compatibility analysis
• Automated polyfill recommendations
• Smart project-wide scanning
• Integrated development workflow

70% faster compatibility checking with actionable results 🚀

📄 License

MIT License © 2025 Mahdiar Kaheh

Built for the developer community - Free to use, modify, and distribute.