WHOIS Lookup API: Domain Registration Data at Scale

What Is WHOIS Data and Why Businesses Need It

WHOIS is a public database protocol that stores domain registration information. When a domain is registered, the registrar records details including the registrant, administrative and technical contacts, registration and expiration dates, name servers, and domain status codes.

For businesses, WHOIS data is essential for:

Domain Portfolio Management

Track expiration dates, monitor registrar changes, and manage renewals across your entire domain portfolio.

Brand Protection

Detect trademark infringement by monitoring new domain registrations that match your brand.

Security Research

Investigate suspicious domains by analyzing registration patterns and name server relationships.

Competitive Intelligence

Monitor competitor domain strategies, new product launches, and infrastructure changes.

WHOIS Data Fields Explained

Field	Description	GDPR Status
domainName	The queried domain	Available
registrar	Domain registrar name	Available
registrationDate	Domain creation date	Available
expirationDate	Domain expiration date	Available
nameServers	Authoritative DNS servers	Available
status	Domain status codes	Available
registrant	Domain owner information	Often redacted
contactEmail	Registrant email	Often redacted

WHOIS Privacy and GDPR Considerations

Since GDPR took effect in May 2018, WHOIS data has undergone significant changes. Registrars now redact personal information (registrant name, email, phone, address) by default for domains registered by EU residents.

What This Means for Your Application

Always handle WHOIS data as potentially GDPR-sensitive
Do not store personal registrant data without a legal basis
Non-personal data (dates, registrar, name servers, status) remains fully accessible
WHOIS APIs aggregate data from multiple sources to maximize available information

Getting Started with the WHOIS Lookup API

Query Domain WHOIS Data

Send a GET request with the target domain name:

curl -X GET "https://api.ops.tools/v1/whois?domain=example.com" \
  -H "Authorization: Bearer YOUR_API_KEY"

Parse the Response

{
  "domainName": "example.com",
  "registrar": "GoDaddy.com, LLC",
  "registrationDate": "1995-08-14T04:00:00Z",
  "expirationDate": "2026-08-13T04:00:00Z",
  "nameServers": ["a.iana-servers.net", "b.iana-servers.net"],
  "status": ["clientDeleteProhibited", "clientTransferProhibited"],
  "daysUntilExpiration": 148,
  "registrarUrl": "https://www.godaddy.com",
  "registrant": {
    "organization": "Internet Corporation for Assigned Names",
    "country": "US"
  }
}

Code Examples

Python

import requests

apiUrl = "https://api.ops.tools/v1/whois"
headers = {"Authorization": "Bearer YOUR_API_KEY"}

response = requests.get(apiUrl, headers=headers, params={"domain": "example.com"})
data = response.json()

print(f"Domain: {data['domainName']}")
print(f"Registrar: {data['registrar']}")
print(f"Expires: {data['expirationDate']}")
print(f"Days remaining: {data['daysUntilExpiration']}")

Node.js

const response = await fetch(
  "https://api.ops.tools/v1/whois?domain=example.com",
  { headers: { "Authorization": "Bearer YOUR_API_KEY" } }
);
const data = await response.json();
console.log(`Domain: ${data.domainName}`);
console.log(`Registrar: ${data.registrar}`);
console.log(`Days until expiry: ${data.daysUntilExpiration}`);

Go

req, _ := http.NewRequest("GET",
    "https://api.ops.tools/v1/whois?domain=example.com", nil)
req.Header.Set("Authorization", "Bearer YOUR_API_KEY")

client := &http.Client{}
resp, _ := client.Do(req)
defer resp.Body.Close()

var result map[string]interface{}
json.NewDecoder(resp.Body).Decode(&result)
fmt.Printf("Domain: %s\n", result["domainName"])
fmt.Printf("Expiry: %s\n", result["expirationDate"])

PHP

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,
    "https://api.ops.tools/v1/whois?domain=example.com"
);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Authorization: Bearer YOUR_API_KEY"
]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
$data = json_decode($response, true);
echo "Domain: " . $data['domainName'];
echo "Expiry: " . $data['expirationDate'];

Domain Expiration Tracking

One of the most valuable uses of a WHOIS API is automated expiration tracking. Losing a domain to expiration can cost thousands in lost revenue, brand damage, and recovery fees.

The Cost of Domain Expiration

Average recovery fee:$200-$2,000

Lost revenue during downtime:$1,000-$100,000+

SEO ranking loss:3-6 months recovery

Brand reputation damage:Incalculable

Check out our domain expiration monitoring guide for a complete automated monitoring implementation.

Bulk WHOIS Lookups for Domain Portfolios

For organizations managing large domain portfolios, the API supports batch operations. Query hundreds of domains efficiently with proper rate limiting and parallel processing.

Bulk WHOIS Best Practices

Cache WHOIS data for 24-48 hours (data changes infrequently)
Space requests 1-2 seconds apart to respect rate limits
Monitor expiration dates in priority order (closest to expiry first)
Set up alerts at 90, 60, 30, and 14 days before expiration
Track registrar changes as potential security indicators

Frequently Asked Questions

Q: What is a WHOIS lookup?

A WHOIS lookup queries a public database that stores domain registration information including the registrar, registrant contact details, registration and expiration dates, name servers, and domain status codes. It is the primary method for finding out who owns a domain.

Q: Is WHOIS data still available after GDPR?

GDPR significantly changed WHOIS data availability. Many registrars now redact personal registrant information. However, registration dates, registrar info, name servers, domain status, and expiration dates remain publicly accessible. WHOIS APIs aggregate data from multiple sources to maximize available information.

Q: How to check domain expiration dates programmatically?

Use a WHOIS lookup API like Ops.Tools to query domain expiration dates. Send a request with the domain name, and the API returns the registration date, expiration date, and days remaining. This enables automated monitoring for domain portfolios. Professional plans start at $29/month.

Q: What is reverse WHOIS lookup?

Reverse WHOIS lookup finds all domains associated with a specific registrant, email address, name server, or IP address. This is useful for competitive research, fraud investigation, and brand protection. The Ops.Tools API supports reverse WHOIS queries by email and name server.