IP Address Lookup
Look up any public IPv4 or IPv6 address: reverse DNS (PTR), location, ISP, ASN, and forward-confirmed reverse DNS.
When IP enrichment runs after a visitor requests details or submits an IP lookup, the IP being looked up is sent to ipwho.is to retrieve ISP, ASN, and location metadata unless request headers already provide the needed visitor network details.
What does an IP address lookup show?
Our IP address lookup checks any public IPv4 or IPv6 address and returns reverse DNS (PTR hostnames), forward-confirmed reverse DNS, approximate location, ISP, ASN, and related network context. Use it for IP address lookup, reverse DNS lookup, email PTR checks, and quick network investigation—without a separate reverse DNS tool.
How to check reverse DNS and FCrDNS
- Enter a public IPv4 or IPv6 address, or select Look up my IP. Private, loopback, and reserved addresses are not supported for explicit lookups.
- Run the lookup. Explicit lookups use ipwho.is for location and network context. Visitor lookups prefer Vercel request headers, with ipwho.is fallback. PTR and forward DNS checks use the platform resolver. Either part can be unavailable independently.
- Read the PTR hostname and its confirmation status. For a mail server, compare the hostname with your intended mail configuration and ask the IP provider to correct missing or mismatched PTR records.
How to interpret the results
- Location, ISP, and ASN
- Approximate location and network context, not a person's identity or street address. A VPN, mobile carrier, or hosting network may appear instead of the user's physical location.
- PTR hostname
- The name returned by reverse DNS. A missing PTR means no reverse record was returned; it does not mean the IP is unused or malicious.
- Forward-confirmed
- The PTR hostname's A record (IPv4) or AAAA record (IPv6) resolves back to the queried address. This checks DNS consistency; it does not prove ownership or guarantee email delivery.
- Not confirmed or not checked
- Not confirmed means the forward lookup did not match. Not checked means the check was inconclusive or skipped. Check resolver availability before treating an inconclusive result as a configuration fault.
Common Use Cases
- Run an IP address lookup for location, ISP, and ASN details
- Perform a reverse DNS lookup (PTR) for any public IP
- Verify email server PTR and forward-confirmed reverse DNS configuration
- Identify the hostname behind an IP address from your logs
- Check the approximate location of an IP accessing your server
- Identify the ISP and ASN associated with a public IP
- Investigate the origin of spam or malicious traffic
- Confirm your own public IP address and location data
Technical references
Frequently Asked Questions
What is reverse DNS lookup?
Reverse DNS lookup (rDNS) maps an IP address to a hostname using a PTR record. Enter a public IP on this page to see PTR hostnames and whether forward DNS confirms them (forward-confirmed reverse DNS).
How do I look up reverse DNS for an IP?
Use this IP address lookup: enter a public IPv4 or IPv6 address and run the lookup. Results include reverse DNS (PTR) hostnames when they exist, plus location, ISP, and ASN context on the same page.
How accurate is IP geolocation?
IP geolocation is approximate. Accuracy varies by database, network, and location; city-level results can be wrong, especially for mobile networks and VPNs. This tool uses ipwho.is for explicit lookups and does not measure an accuracy percentage. ISP and ASN fields identify network context, not an individual.
Can I look up any IP address?
Yes, you can look up any valid public IPv4 or IPv6 address. Private IP addresses (like 192.168.x.x or 10.x.x.x) cannot be geolocated as they are not routable on the internet.
What is an ASN (Autonomous System Number)?
An ASN is a unique identifier assigned to networks (like ISPs or large organizations) that participate in internet routing. It helps identify who manages a particular IP address block.
Why is reverse DNS important for email?
Many email servers check that the sending IP has forward-confirmed reverse DNS: the PTR hostname resolves back to the same IP. Missing or mismatched PTR records often cause emails to be marked as spam or rejected entirely.
Why doesn't my IP have a reverse DNS record?
PTR records must be set up by whoever controls the IP address—usually your ISP or hosting provider. Many residential ISPs don't configure reverse DNS by default. Contact your provider to request PTR record setup.
Can I set my own reverse DNS?
PTR records are managed by the operator of the IP address space or a delegated administrator. Contact your ISP or hosting provider; some providers offer a reverse DNS setting for eligible public IPs. Adding a PTR to your domain's ordinary DNS zone does not change the reverse record for your IP.