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miccho27
miccho27

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Free WHOIS & DNS Lookup API — Build Domain Tools Without Scraping

#api #dns #webdev #security

Building a domain lookup tool? A competitor analysis dashboard? A phishing detection system? You need WHOIS and DNS data, but:

  • WHOIS servers rate-limit aggressively
  • Parsing WHOIS text responses is a nightmare (every TLD has different formats)
  • Most WHOIS APIs charge $50+/month

I built a free API that returns structured JSON for WHOIS lookups, DNS records, and domain availability — all via Cloudflare's DoH (DNS over HTTPS) for reliability.

Endpoints

Endpoint Method Description
/whois?domain= GET WHOIS/RDAP lookup with structured JSON output
/dns?domain=&type= GET DNS records (A, AAAA, MX, TXT, NS, CNAME, SOA)
/available?domain= GET Domain availability check
/bulk POST Bulk lookup (up to 10 domains)

Quick Example — Domain Investigation

Python 

import requests

headers = {
    "X-RapidAPI-Key": "YOUR_KEY",
    "X-RapidAPI-Host": "whois-domain-api.p.rapidapi.com"
}

whois = requests.get(
    "https://whois-domain-api.p.rapidapi.com/whois?domain=example.com",
    headers=headers
).json()

print(f"Registrar: {whois['registrar']}")
print(f"Created: {whois['creation_date']}")
print(f"Expires: {whois['expiration_date']}")
print(f"Name Servers: {whois['name_servers']}")

# DNS records
dns = requests.get(
    "https://whois-domain-api.p.rapidapi.com/dns?domain=example.com&type=MX",
    headers=headers
).json()

for record in dns["records"]:
    print(f"MX: {record['value']} (priority: {record['priority']})")
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JavaScript — Bulk Domain Check 

const response = await fetch(
  "https://whois-domain-api.p.rapidapi.com/bulk",
  {
    method: "POST",
    headers: {
      "X-RapidAPI-Key": "YOUR_KEY",
      "X-RapidAPI-Host": "whois-domain-api.p.rapidapi.com",
      "Content-Type": "application/json"
    },
    body: JSON.stringify({
      domains: ["startup.io", "myapp.dev", "coolproject.com"]
    })
  }
);
const results = await response.json();
results.forEach(d => console.log(`${d.domain}: ${d.available ? "Available!" : "Taken"}`));
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Real-World Use Cases

  1. Domain Flipping Tool — Check expiration dates in bulk, find expiring domains
  2. Phishing Detection — Flag recently registered domains impersonating your brand
  3. Competitor Analysis — Monitor DNS changes (CDN switches, email provider changes)
  4. DevOps Monitoring — Alert on SSL cert expiry, DNS propagation verification
  5. Sales Intelligence — Identify a company's tech stack from DNS/MX records

How It Compares

Feature WHOIS Domain API WhoisXML API DomainTools Whoxy
Free tier 500 req/mo 500 req/mo None 1000 credits
JSON output Yes Yes Yes Yes
DNS records Included Separate API Included No
Bulk lookup 10/request 1/request Paid only Paid
Domain availability Included Separate Paid No
Price (paid) $5.99/mo $19/mo $99/mo $2/1000

Try It Free

  1. WHOIS Domain API on RapidAPI
  2. Subscribe free (500 req/month)
  3. Test any domain instantly

What domain analysis features would be most useful? Let me know in the comments.

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