IP Lookup and Geolocation Tools

IP lookup returns information about an IP address including location, ISP, and other metadata.

IP Address Types

IPv4

192.168.1.1
8.8.8.8

IPv6

2001:4860:4860::8888
2607:f8b0:4009::b

Public vs Private IPs

| Range | Type | Example | |-------|------|---------| | 10.0.0.0 - 10.255.255.255 | Private | 10.0.0.1 | | 172.16.0.0 - 172.31.255.255 | Private | 172.16.0.1 | | 192.168.0.0 - 192.168.255.255 | Private | 192.168.1.1 | | Rest | Public | 8.8.8.8 |

IP Lookup Services

Using ip-api.com (free)

// Note: Requires backend proxy to avoid CORS
async function lookupIP(ip) {
  const response = await fetch(`http://ip-api.com/json/${ip}`);
  return response.json();
}

// Example response
{
  status: "success",
  country: "United States",
  countryCode: "US",
  region: "CA",
  regionName: "California",
  city: "Mountain View",
  lat: 37.386,
  lon: -122.084,
  timezone: "America/Los_Angeles",
  isp: "Google LLC",
  org: "Google Public DNS",
  as: "AS15169 Google LLC"
}

Using ipinfo.io

const response = await fetch(`https://ipinfo.io/${ip}/json`);
const data = await response.json();
// { ip, city, region, country, org, ... }

Browser Client Info

// Get user's IP (from server)
app.get('/my-ip', (req, res) => {
  res.json({
    ip: req.ip || req.connection.remoteAddress,
    headers: req.headers['x-forwarded-for']
  });
});

IP Validation

function isValidIPv4(ip) {
  const parts = ip.split('.');
  if (parts.length !== 4) return false;
  return parts.every(part => {
    const num = parseInt(part, 10);
    return num >= 0 && num <= 255 && part === num.toString();
  });
}

function isValidIPv6(ip) {
  // Simplified check
  return /^[0-9a-fA-F:]+$/.test(ip) && ip.includes(':');
}

Common Use Cases

1. Analytics

function getVisitorLocation(req) {
  return {
    ip: req.ip,
    country: req.headers['cf-ipcountry'], // Cloudflare
    city: req.headers['x-vercel-ip-city'] // Vercel
  };
}

2. Content Localization

async function getLocalizedContent(ip) {
  const { country } = await lookupIP(ip);
  
  if (country === 'DE') return germanContent;
  if (country === 'FR') return frenchContent;
  return englishContent;
}

3. Rate Limiting by IP

const rateLimit = new Map();

function checkRateLimit(ip) {
  const now = Date.now();
  const requests = rateLimit.get(ip) || [];
  
  // Remove old requests
  const recent = requests.filter(t => now - t < 60000);
  
  if (recent.length > 100) {
    throw new Error('Rate limit exceeded');
  }
  
  recent.push(now);
  rateLimit.set(ip, recent);
}

Limitations

• Inaccurate - IP location can be wrong by hundreds of miles
• VPN/Proxy - Shows VPN location, not real location
• Mobile - Often shows ISP headquarters
• Privacy - Can be blocked or spoofed

Free APIs

| Service | Limits | |---------|--------| | ip-api.com | 45 requests/min | | ipinfo.io | 50K requests/month | | ipgeolocation.io | 1500 requests/day | | ipapi.co | 10K requests/month |

Conclusion

Use IP lookup for analytics and basic geolocation. Don't rely on it for security - it's easily spoofed. Combine with other signals for better accuracy.