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SiteCheck Web Intel – Reverse DNS PTR Lookup
x402
SiteCheck Web Intel – Reverse DNS PTR Lookup is a paid API for AI agents from api.webintel-api.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-24).
Returns PTR (reverse DNS) records for an IPv4 address and validates whether each PTR hostname resolves back to the same IP via forward-confirmed reverse DNS (FCrDNS).
Price / call$0.002
Success—
StatusUnknown
How this service works
Reverse DNS (PTR) names for an IPv4 address, and forward-confirmed reverse DNS: whether each PTR name resolves back (A record) to the same address. Up to 3 PTR names are checked. Many addresses have no PTR record; that is a normal answer.
Output
Returns up to 3 PTR hostnames associated with the given IPv4 address, along with a forward-confirmed reverse DNS (FCrDNS) check for each: whether the PTR hostname's A record resolves back to the original IP. If no PTR record exists, the response indicates that clearly as a normal (non-error) result.
Example use cases
Email server PTR validation
“Check the reverse DNS PTR record for 203.0.113.45 and confirm whether the PTR hostname resolves back to that IP — I need to know if it's forward-confirmed for email deliverability checks.”
Threat intel IP attribution
“I've got a suspicious IP address 185.220.101.12 showing up in my logs — can you look up its PTR record and tell me what hostname it maps to, and whether that hostname forward-confirms back to the same IP?”
Network infrastructure audit
“For the IP 104.21.3.100, what are the PTR names returned by reverse DNS, and do any of them pass forward-confirmed reverse DNS validation?”
Technical details
Endpoint
GEThttps://api.webintel-api.workers.dev/api/security/reverse-dns-ptr?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to resolve the hostname(s) associated with an IPv4 address via reverse DNS (PTR records) and additionally want to validate forward-confirmed reverse DNS (FCrDNS). Ideal for email server reputation checks, network security investigations, IP attribution in threat intelligence, or infrastructure audits. Prefer this over generic WHOIS or geolocation tools when the specific question is about DNS PTR records and hostname verification.
Side effects
- Invalid or malformed IPv4 address input returns an error
- IP address with no PTR record returns an empty or null PTR list (normal, not an error)
- DNS timeout or upstream resolver failure may result in incomplete results
- Private/reserved IP ranges may not have PTR records
- PTR name exists but A record lookup times out, resulting in unconfirmed FCrDNS status
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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