Reverse DNS Lookup
Enter an IPv4 or IPv6 address to see the hostname it points to, whether that hostname points back, and who controls the record.
Asking public resolvers about 216.73.217.145…
What is reverse DNS?
Ordinary DNS answers the question “what IP address does this name use?” Reverse DNS (rDNS) answers the opposite one: “what name belongs to this IP address?” The answer lives in a PTR record, and it gets published by whoever owns the address block, not by whoever owns a website. That one detail explains nearly every reverse DNS headache you'll run into.
Most people never think about it until something breaks: a mail server whose messages land in spam, a log full of bare IP addresses, a firewall rule that needs a hostname. A reverse lookup turns a number into a clue.
How this reverse DNS lookup works
We flip the address
Your IP is rewritten into a special lookup name: the octets backwards under in-addr.arpa for IPv4, every hex digit backwards under ip6.arpa for IPv6. 8.8.8.8 becomes 8.8.8.8.in-addr.arpa.
Three resolvers get asked
We ask a PTR question to Cloudflare, Google and Quad9 separately. If they disagree, or one is having a bad day, you'll see exactly which one said what.
The hostname gets checked back
A PTR record is only a claim. We look up the hostname's A and AAAA records to see whether it really points back at the IP you started with.
We find who runs it
We trace which reverse zone the IP lives in and who its network owner is, because that's the party who can actually change the record.
How to read your result
- Forward-confirmed
- The IP has a hostname and that hostname points straight back. This is the healthy state, and the one mail servers want to see.
- Not confirmed
- A PTR record exists, but the hostname it names resolves somewhere else, or nowhere. The two halves of the setup don't agree, so fix the A or AAAA record, or the PTR.
- No PTR record
- Nobody has published a hostname for this IP. Normal for most home connections and plenty of servers, a problem if it sends email.
- Lookup failed
- The resolvers timed out or returned errors. That is not the same as there being no record, so give it another go before drawing a conclusion.
Why reverse DNS matters for email
Receiving mail servers look up the PTR record of every server that connects to them. No record, or a name that doesn't resolve back to the sender, counts against it in spam scoring, and some servers refuse the connection outright. Gmail's sender guidelines ask for valid forward and reverse DNS on the IP you send from, so it's one of the first things worth checking when a mailbox provider starts rejecting you.
The hostname matters too. A name like mail.yourdomain.com reads as deliberate. One stuffed with the IP or a word like “dynamic” reads as an ISP default, and we flag those when we spot them. Reverse DNS is only one piece of deliverability, next to SPF, DKIM and DMARC. It won't fix a bad sending reputation, but a missing PTR can sink an otherwise good setup.
How to set or fix a PTR record
You can't add a PTR record at your domain registrar or in the DNS zone for your domain, and this trips up a lot of people. The reverse zone belongs to the IP owner, so the change has to be made by them. In practice that means one of these:
- VPS and cloud hosts. Many have a reverse DNS field on the IP in the dashboard (Hetzner, Vultr and Linode work this way). DigitalOcean takes the PTR from the Droplet's name, so you name the Droplet after the hostname. AWS handles Elastic IPs through a request form.
- Dedicated servers and colocation. Usually a support ticket, or a control panel if the provider offers one.
- Business internet lines. Ask your ISP. Many will set it for a static IP; consumer plans often won't.
Set the PTR to the hostname your server actually uses, make sure that hostname has an A (or AAAA) record pointing at the same IP, then check back here. The result above spells out which half is wrong if it still isn't confirmed. Not sure who owns the address? The WHOIS lookup shows the network owner and the abuse contact.
Reverse DNS vs. reverse IP lookup
The names sound alike, but they answer different questions. Reverse DNS returns the hostname published for an IP, a single record set by the IP's owner. A “reverse IP lookup” lists every website that happens to be hosted on an IP, which can't be read from DNS and needs a crawled dataset. This tool does the first. To go from a name to its addresses, use DNS Lookup, and to see how those records look from resolvers around the world, try DNS Checker.
Frequently asked questions
What is a reverse DNS lookup?
It's a DNS query that starts with an IP address and asks for the hostname registered to it. Normal DNS goes from name to address; reverse DNS goes the other way, using PTR records stored in the in-addr.arpa and ip6.arpa zones.
Why does my IP address have no reverse DNS?
Because nobody has created a PTR record for it. Reverse DNS is optional and has to be set up by whoever owns the IP block, which is usually your internet provider or hosting company. Most residential connections never get one, and plenty of cloud servers don't until you ask.
What does NXDOMAIN mean in a reverse lookup?
It means the reverse name itself doesn't exist, so there is no PTR record to return. You may also see NOERROR with no answer, which says the name exists but holds no PTR. For practical purposes both mean the same thing: no hostname is published for that IP.
What is forward-confirmed reverse DNS (FCrDNS)?
It's a round trip. The IP's PTR record names a host, and that host's A or AAAA record names the same IP. Mail servers use it as a cheap sanity check that whoever controls the IP also controls the name it claims.
Can I change my own reverse DNS record?
Only if you control the IP address. If you rent a server, the setting is normally in your hosting provider's dashboard or behind a support request. Your domain registrar and the DNS host for your domain can't do it, since the reverse zone belongs to the IP owner, not to your domain.
Can one IP address have more than one PTR record?
Yes, the DNS allows it. It's rarely a good idea. Software that reads PTR records often looks at only one, and which one it picks can vary, so most guides recommend a single record that matches your mail server's hostname.
How long does a reverse DNS change take to show up?
Until the old answer's TTL runs out in each resolver's cache. That's often an hour or less, sometimes a day. If your lookup still shows the old hostname, the TTL on this page tells you roughly how long the cached copy can live.
Does this work for IPv6 addresses?
Yes. IPv6 reverse names are built from the full 32-digit address written backwards under ip6.arpa, which is why they look so long. We build that name for you, and the zone and name servers shown are for the address's own delegation.