Reverse DNS lookup
Enter any IPv4 or IPv6 address to find its PTR (reverse DNS) record — the hostname its owner has published — straight from your browser over encrypted DNS-over-HTTPS. No install, nothing stored.
Enter an IPv4 or IPv6 address to look up its reverse DNS (PTR) record — the hostname the IP's owner has published for it. Runs in your browser over encrypted DNS-over-HTTPS. Nothing is stored.
A PTR record is set by whoever controls the IP address block, so it can be missing, generic (like host-1-2-3-4.example.net), or point somewhere unrelated to a site's forward DNS. Treat it as a hint, not proof of identity. Queries run in your browser via Cloudflare DNS-over-HTTPS.
What a reverse DNS lookup tells you
Reverse DNS (PTR) lookup
A reverse DNS lookup takes an IP address and returns the hostname its owner has published for it, stored as a PTR record. It's the mirror image of a normal lookup, which turns a hostname into an IP.
How reverse DNS works
DNS reads names from most specific to least specific — right to left. To make IP addresses
fit that model, reverse lookups use two special zones. IPv4 addresses live under
in-addr.arpa with the octets reversed: the address 8.8.4.4 becomes the
query 4.4.8.8.in-addr.arpa. IPv6 addresses live under ip6.arpa,
with every hex digit of the fully expanded address reversed and separated by dots. This tool
builds that query name for you, then asks a public resolver for the PTR record over
encrypted DNS-over-HTTPS — the request goes straight from your browser to the resolver, so
we never see the addresses you check.
When network enrichment is available, the tool also shows the IP's country and city, ISP, organization, and autonomous system (AS) number, plus whether the address looks like a mobile, proxy/VPN, or hosting/datacenter connection. Those come from a third-party IP-geolocation database: reliable for the network operator and ASN, but only approximate for city-level location. If the enrichment endpoint isn't configured, the tool simply shows the PTR record and nothing else.
What people use reverse DNS for
- Mail server checks
- Many mail servers reject or downgrade mail from an IP whose PTR is missing or doesn't match its forward (A/AAAA) record. Sending admins check reverse DNS to keep delivery clean.
- Reading server logs
- Turning raw IPs in access and firewall logs into hostnames makes traffic easier to skim — you can often tell a cloud provider, ISP, or crawler apart at a glance.
- Network troubleshooting
- Tools like traceroute show PTR names for each hop, which reveal the carriers and datacenters a packet passes through.
- Abuse and spam investigation
- A generic or absent PTR is one weak signal among many when triaging a suspicious connection — never proof on its own.
Honest limitations
Reverse DNS is genuinely useful, but it's easy to over-trust. A few things worth keeping in mind: a PTR record is optional and is simply whatever text the IP block's operator chose to publish — it isn't checked against anything, so it can say almost anything and can't prove who owns an address. A missing PTR is completely normal, especially for residential, mobile, and many cloud IPs, and doesn't mean the address is fake or malicious. Because forward and reverse DNS are maintained separately, they frequently disagree, and that's expected outside of specific cases like mail servers. For authoritative answers about who holds an IP, check its WHOIS/RDAP registration and its autonomous system rather than relying on the PTR alone.
Reverse DNS lookup — frequently asked questions
What is a reverse DNS (PTR) lookup?
A forward DNS lookup turns a hostname into an IP address. A reverse lookup does the opposite: it takes an IP and asks DNS what hostname, if any, the IP's owner has published for it. That mapping lives in a PTR (pointer) record in a special reverse zone.
Why does an IP have no PTR record?
Reverse DNS is optional, and the owner of the IP block controls it — not the owner of the website. Most residential, mobile, and many cloud IPs simply have no PTR record, or have a generic auto-generated one. A missing PTR is normal and usually not a problem unless the IP is running a mail server.
Why doesn't the PTR match the website's domain?
Forward and reverse DNS are maintained separately, often by different parties. A site's A record is set by the domain owner, while the PTR is set by whoever runs the IP block (frequently the hosting provider). So example.com might resolve to an IP whose PTR is something like server42.hostingcompany.net. That's expected — the two only have to match for specific cases like mail servers.
Can I trust a PTR record as proof of who owns an IP?
No. A PTR is just text the IP block's operator chose to publish; it isn't verified against anything and can say almost anything. Treat it as a hint. For authoritative ownership, look up the IP's WHOIS/RDAP registration and its autonomous system (AS), which this tool shows when network enrichment is available.
What are in-addr.arpa and ip6.arpa?
They're the special DNS zones that hold reverse records. An IPv4 address like 8.8.4.4 is looked up as 4.4.8.8.in-addr.arpa — the octets reversed, because DNS reads names from most to least specific. IPv6 uses ip6.arpa with each hex digit reversed and dotted. This tool builds that query name for you automatically.
Do you store the IPs I look up?
No. The PTR query runs in your browser directly against a public DNS-over-HTTPS resolver. If network enrichment is enabled, the IP is sent once to our edge endpoint to fetch geolocation and ASN details, which we don't log. We never store the addresses you check.