DNS Lookup APIs
DNS lookup APIs return a domain's records programmatically, often alongside related network data. HackerTarget answers DNS, reverse DNS and ASN queries as plain text without a key, and NetworkCalc adds SPF checks and subnet math. SecurityTrails keeps historical DNS and WHOIS for threat research, while Host.io links DNS records with backlinks and related domains across 600M+ registered domains.
| API | Pricing | Auth | Format | Free tier | Status |
|---|---|---|---|---|---|
Domain IntelligenceWHOIS/RDAP, DNS, SSL certificate, subdomain and SPF/DMARC/DKIM data for a domain in one call. Developer Tools › WHOIS & DNS | Freemium | API key | JSON | <100/day | Live |
DomScanDomain, DNS, WHOIS/RDAP, TLS, typosquatting and brand-monitoring lookups across 1,100+ TLDs. Developer Tools › WHOIS & DNS | Freemium | API key | JSON | — | Live |
HackerTarget IP Tools APIASN, DNS, reverse DNS/IP, WHOIS, GeoIP, HTTP header and subnet lookups for any IP or domain as plain text. Developer Tools › WHOIS & DNS | Freemium | None | CSV | <100/day | Live |
Host.ioDNS records, backlinks, IP/ASN and related-domain data across 600M+ registered domains. Developer Tools › WHOIS & DNS | Freemium | API key | JSON | <100/day | Live |
NetworkCalcREST utilities for IP subnet math, DNS/WHOIS/SPF lookups, TLS certificate checks, and encoding conversions. Developer Tools › WHOIS & DNS | Freemium | None | JSON | — | Live |
SecurityTrailsCurrent and historical DNS, WHOIS and domain/IP intelligence for security and threat-research tools. Identity & Security › Threat Intel | API key | JSON | — | Live |
Domain IntelligenceFreemiumLive
WHOIS/RDAP, DNS, SSL certificate, subdomain and SPF/DMARC/DKIM data for a domain in one call.
API key · JSON
<100/day
no machine-readable spec
DomScanFreemiumLive
Domain, DNS, WHOIS/RDAP, TLS, typosquatting and brand-monitoring lookups across 1,100+ TLDs.
API key · JSON
—
OpenAPI spec · llms.txt
HackerTarget IP Tools APIFreemiumLive
ASN, DNS, reverse DNS/IP, WHOIS, GeoIP, HTTP header and subnet lookups for any IP or domain as plain text.
None · CSV
<100/day
no machine-readable spec
Host.ioFreemiumLive
DNS records, backlinks, IP/ASN and related-domain data across 600M+ registered domains.
API key · JSON
<100/day
no machine-readable spec
NetworkCalcFreemiumLive
REST utilities for IP subnet math, DNS/WHOIS/SPF lookups, TLS certificate checks, and encoding conversions.
None · JSON
—
llms.txt
SecurityTrailsLive
Current and historical DNS, WHOIS and domain/IP intelligence for security and threat-research tools.
API key · JSON
—
no machine-readable spec
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Choosing a DNS Lookup API
Is there a free DNS Lookup API?
Yes. HackerTarget IP Tools API, Host.io, Domain Intelligence, DomScan and NetworkCalc have a free tier alongside paid plans.
Which DNS Lookup APIs work without an API key?
HackerTarget IP Tools API and NetworkCalc need no key or sign-up, so you can try them with a plain request.
Can I call a DNS Lookup API from front-end JavaScript?
HackerTarget IP Tools API and NetworkCalc allow cross-origin requests and need no key, so they work straight from the browser. For the others, call them from your server so your key stays private.
Can I use DNS Lookup APIs in a commercial project?
DomScan permits commercial use.
Which DNS Lookup APIs work with AI agents?
DomScan publishes an OpenAPI spec for generating clients and tools.
Broader: WHOIS & DNS APIs · Developer Tools APIs
More in WHOIS & DNS: Domain Availability APIs