Free DNS Lookup API — Resolve, WHOIS & Domain Availability

Need to resolve DNS records, check domain availability, or run WHOIS lookups from your code? The Agent DNS Lookup API gives you programmatic access to DNS resolution, reverse lookups, RDAP/WHOIS data, domain availability checks, and propagation monitoring — all through a clean REST interface with no account required.

This guide covers every endpoint: A/AAAA/MX/TXT/CNAME resolution, reverse DNS, WHOIS, domain availability, propagation across 8 global resolvers, and batch lookups for up to 50 domains at once.

Quick Start — Resolve a Domain

# Resolve A + AAAA records
curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/resolve/google.com

{
  "domain": "google.com",
  "ipv4": ["142.251.116.139", "142.251.116.101", "142.251.116.113"],
  "ipv6": ["2607:f8b0:4023:1009::64", "2607:f8b0:4023:1009::8b"],
  "queryTime": 8,
  "timestamp": "2026-03-03T20:22:00.123Z"
}

import requests

BASE = "https://agent-gateway-kappa.vercel.app/v1/agent-dns"

# Resolve A + AAAA records
resp = requests.get(f"{BASE}/api/resolve/google.com")
data = resp.json()

for ip in data["ipv4"]:
    print(f"IPv4: {ip}")
for ip in data["ipv6"]:
    print(f"IPv6: {ip}")

const BASE = "https://agent-gateway-kappa.vercel.app/v1/agent-dns";

const resp = await fetch(`${BASE}/api/resolve/google.com`);
const data = await resp.json();

console.log("IPv4:", data.ipv4);
console.log("IPv6:", data.ipv6);
console.log("Query time:", data.queryTime, "ms");

No API key needed for basic lookups. The free tier gives you generous rate limits out of the box.

API Endpoints

Look Up Specific Record Types

Query any DNS record type by appending it to the resolve endpoint:

MX Records (Mail Servers)

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/resolve/google.com/MX

{
  "domain": "google.com",
  "type": "MX",
  "records": [
    {"exchange": "smtp.google.com", "priority": 10}
  ],
  "queryTime": 11
}

TXT Records (SPF, DKIM, verification)

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/resolve/github.com/TXT

{
  "domain": "github.com",
  "type": "TXT",
  "records": [
    "v=spf1 ip4:192.30.252.0/22 include:_netblocks.google.com ...",
    "MS=ms58704441",
    "docusign=...",
    "atlassian-domain-verification=..."
  ]
}

NS Records (Nameservers)

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/resolve/cloudflare.com/NS

{
  "domain": "cloudflare.com",
  "type": "NS",
  "records": ["ns3.cloudflare.com", "ns4.cloudflare.com", "ns5.cloudflare.com", "ns6.cloudflare.com", "ns7.cloudflare.com"]
}

Reverse DNS Lookup

Convert an IP address back to its hostname:

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/reverse/8.8.8.8

{
  "ip": "8.8.8.8",
  "hostnames": ["dns.google"],
  "queryTime": 2
}

WHOIS / RDAP Lookup

Get registration details for any domain — registrar, creation date, expiration, nameservers, and DNSSEC status:

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/whois/example.com

{
  "domain": "example.com",
  "registered": true,
  "registrar": "RESERVED-Internet Assigned Numbers Authority",
  "nameservers": ["ELLIOTT.NS.CLOUDFLARE.COM", "HERA.NS.CLOUDFLARE.COM"],
  "status": ["client delete prohibited", "client transfer prohibited"],
  "created": "1995-08-14T04:00:00Z",
  "updated": "2026-01-16T18:26:50Z",
  "expires": "2026-08-13T04:00:00Z",
  "dnssec": true
}

Domain Availability Check

Check whether a domain is registered or available for purchase:

# Check if a domain is available
curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/check/my-cool-startup.com

{
  "domain": "my-cool-startup.com",
  "available": true,
  "registered": false,
  "hasRecords": false,
  "ips": [],
  "registrar": null,
  "expires": null,
  "queryTime": 208
}

The availability check combines DNS resolution with RDAP queries. If a domain has no DNS records and no RDAP registration, it's marked as available.

DNS Propagation Check

After making DNS changes, verify propagation across 8 global resolvers:

curl https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/propagation/example.com

{
  "domain": "example.com",
  "results": [
    {"resolver": "8.8.8.8", "name": "Google", "ips": ["93.184.216.34"], "queryTime": 5},
    {"resolver": "1.1.1.1", "name": "Cloudflare", "ips": ["93.184.216.34"], "queryTime": 3},
    {"resolver": "9.9.9.9", "name": "Quad9", "ips": ["93.184.216.34"], "queryTime": 8},
    {"resolver": "208.67.222.222", "name": "OpenDNS", "ips": ["93.184.216.34"], "queryTime": 12},
    {"resolver": "185.228.168.9", "name": "CleanBrowsing", "ips": ["93.184.216.34"], "queryTime": 15}
  ],
  "consistent": true,
  "totalResolvers": 8
}

The consistent field tells you whether all resolvers agree on the same answer — useful after updating A records, switching nameservers, or migrating hosting.

Batch DNS Resolution

Resolve up to 50 domains in a single request:

curl -X POST https://agent-gateway-kappa.vercel.app/v1/agent-dns/api/batch \
  -H "Content-Type: application/json" \
  -d '{
    "domains": ["google.com", "github.com", "cloudflare.com"],
    "type": "A"
  }'

{
  "results": [
    {"domain": "google.com", "records": ["142.251.116.139", "142.251.116.101"]},
    {"domain": "github.com", "records": ["140.82.121.4"]},
    {"domain": "cloudflare.com", "records": ["104.16.132.229", "104.16.133.229"]}
  ],
  "total": 3,
  "queryTime": 24
}

Real-World Use Cases

Comparison: Free DNS API vs Alternatives

Key advantage: Agent DNS combines DNS resolution, WHOIS, availability checks, and propagation monitoring in a single API — most alternatives only offer one or two of these features, and lock the rest behind paid plans.

FAQ