WhoisJSON API Reference & Integration Guide
Everything you need to integrate WHOIS, DNS, SSL, and domain availability data into your applications. One API key, six endpoints, structured JSON or XML responses.
Quick Start Guide
Get your first API response in under two minutes. All you need is a free account and a single HTTP request.
Sign up — your API key is generated instantly.
Authorization: TOKEN=YOUR_API_KEY
Base URL: https://whoisjson.com/api/v1
# WHOIS lookup
curl -s "https://whoisjson.com/api/v1/whois?domain=example.com" \
-H "Authorization: TOKEN=YOUR_API_KEY"
# DNS records
curl -s "https://whoisjson.com/api/v1/nslookup?domain=example.com" \
-H "Authorization: TOKEN=YOUR_API_KEY"
# Domain availability
curl -s "https://whoisjson.com/api/v1/domain-availability?domain=example.com" \
-H "Authorization: TOKEN=YOUR_API_KEY"
# SSL certificate check
curl -s "https://whoisjson.com/api/v1/ssl-cert-check?domain=example.com" \
-H "Authorization: TOKEN=YOUR_API_KEY"
# Subdomains
curl -s "https://whoisjson.com/api/v1/subdomains?domain=example.com" \
-H "Authorization: TOKEN=YOUR_API_KEY"
format=xml parameterRemaining-Requests header in every response_forceRefresh=1 to bypass cache (costs 2x credits)Six Endpoints, One Token
All endpoints share the same base URL and authentication. Your free plan includes 1,000 requests/month across all services.
WHOIS Lookup
Query domain registration data — registrar, dates, nameservers, status codes, and contact information.
domain (required) — domain nameDNS Records
Resolve A, AAAA, MX, TXT, CNAME, NS, SOA records for any domain in a single call.
domain (required) — domain nameSSL Certificate
Validate SSL/TLS certificates — issuer, validity period, encryption standard, and chain of trust.
domain (required) — domain nameDomain Availability
Real-time registration status check. Returns whether a domain is available or already registered.
domain (required) — domain nameSubdomain Discovery
Find active subdomains using parallel DNS brute-force with wildcard detection. Returns A & CNAME records.
domain (required) — domain nameReverse WHOIS
Discover all domains associated with a given IP address, sourced from our private database.
ip (required) — IP addressHTTP Status Codes
The API uses standard HTTP status codes to indicate success or failure. Every response includes a Remaining-Requests header so you can track your usage in real time.
| Code | Description | Reason |
|---|---|---|
| 200 | Successful operation | Request processed successfully |
| 400 | Bad Request | Invalid request parameters |
| 401 | Unauthorized | Invalid or missing API token |
| 403 | Access Denied | Email address not validated |
| 429 | Limit Exceeded | Monthly quota or rate limit reached |
| 500 | Internal Error | Server-side issue — retry later |
Official Client Libraries
Install our official SDK for your preferred language and start querying in minutes.
PHP Client
Composer package for Laravel, Symfony, and vanilla PHP projects.
composer require whoisjson/whoisjsonPython Client
pip package compatible with Python 3.7+ — Django, Flask, FastAPI, scripts.
pip install whoisjsonNode.js Client
npm package for Express, Next.js, Fastify, and any Node.js project.
npm install @whoisjson/whoisjsonTry It Yourself
Explore every endpoint, inspect request parameters and response schemas, and test live API calls directly from this page.
A RESTful API Designed for Developers
WhoisJSON provides a unified RESTful API for domain intelligence. All six endpoints — WHOIS lookup, DNS records, SSL certificate validation, domain availability, subdomain discovery, and reverse WHOIS — share the same base URL, authentication method, and response format. Whether you are building a cybersecurity tool in Python, a domain management dashboard in Node.js, or a registration pipeline in PHP, our API integrates in minutes with predictable URLs, standard HTTP methods, and clear error codes.
Authentication & Rate Limits
Every API call requires a single Authorization: TOKEN=YOUR_API_KEY header. Your token is generated instantly when you create a free account. The free plan includes 1,000 requests per month shared across all endpoints with a rate limit of 20 requests per minute. Need more? Our paid plans scale up to unlimited requests with rate limits of 300 req/min. Check the Remaining-Requests header in every API response to monitor your usage in real time.
Caching, Formats & Advanced Features
Responses are cached for performance (3-hour TTL). Add force=1 to any request to bypass the cache and get fresh data (costs 2x credits on most plans). All endpoints return JSON by default; append format=xml if your stack requires XML. Our WHOIS engine supports RDAP, the next-generation domain data protocol, and covers over 1,500 TLDs and country-code TLDs. For monitoring use cases, explore our Domain Monitoring service that tracks WHOIS, DNS, and SSL changes and sends alerts automatically.
Ready to Start Building?
Create your free account, grab your API key, and make your first call in under two minutes.