Free Domain API Documentation
Free RESTful APIs for domain research. Access WHOIS data, DNS records, domain scoring, and more programmatically.
Free Domain Lookup API — No Key Required
Whose.Domains provides a free, open REST API for domain research and network intelligence. Whether you are building a domain monitoring tool, running automated WHOIS lookups, screening expiring domains at scale, or investigating phishing infrastructure — our API gives you programmatic access to the same data powering this site, with no registration or API key required for standard usage.
All endpoints return structured JSON, making integration straightforward in any language or platform. Use it from Python scripts, Node.js services, shell pipelines, browser extensions, or security automation workflows.
Automate domain availability checks, enrich user-submitted domains with WHOIS data, monitor DNS changes, or validate email addresses against live MX records.
Investigate phishing domains, pivot from an IP to all hosted domains via reverse IP lookup, compare WHOIS snapshots to detect registrant changes, and assess domain health scores.
Batch-screen expiring domain lists, pull WHOIS history for due diligence, estimate domain valuation, and export full domain reports as JSON for offline analysis.
Domain Lookup
Looks up domain WHOIS information. Triggers a fresh WHOIS query if data is not cached. Returns RDAP URL if applicable.
domainName - Full domain name (e.g., example.com)Response:
{"code":0, "data": {"rdapUrl": "..."}} on success
Domain Health Score
Comprehensive domain health scoring (0-100) with grade (A+ to F). Evaluates SSL, DNS, email security (SPF/DKIM/DMARC), security headers, and domain age.
totalScore, grade, categories (each with score and recommendations)
WHOIS Compare
Compare two domains side by side — registration data, DNS, ownership. Includes a similarity score (0-100) indicating likelihood of same ownership.
domain1, domain2Response: Profiles for both domains, field-by-field differences, similarity score
DNS Analysis
Deep DNS analysis: NS, A, AAAA, MX, TXT, SOA, CNAME records. Also checks SPF, DMARC, DKIM and detects configuration issues.
Domain Analysis
Full domain analysis including technical metrics (response time, SSL, server software, open ports), SEO analysis (title, meta, headings, links, Open Graph), and security assessment (security headers, security.txt, SSL details).
WHOIS History & Diff
List all WHOIS snapshots for a domain.
Compare two WHOIS snapshots and see field-by-field changes.
Automatically compare the two most recent snapshots of a domain.
Domain Report Export
Download a comprehensive JSON report including WHOIS, registrant, DNS records, subdomains, and WHOIS history snapshots. Response has Content-Disposition: attachment header.
Expiring Domains
List domains expiring within a specified number of days. Supports TLD filtering and pagination.
days (1-365, default 30), page (default 1), tld (optional, e.g. "com")
Reverse IP Lookup
Find all domains hosted on a given IPv4 address. Includes GeoIP and ASN information.
Bulk Domain Search
Check up to 100 domains at once for availability, WHOIS info, or DNS status.
{"domains": ["example.com", "test.org"], "searchType": "availability"}
searchType options:
availability, whois, dns
Response Format
All API responses follow this structure:
{
"code": 0, // 0 = success, 400 = error
"msg": "...", // Error message (if any)
"data": { ... } // Response payload
}