Reverse DNS Lookup
Find the hostname behind an IP address — and check that the hostname points back to the same address, the test mail servers use before they accept your email.
Up to 25 addresses at a time. Queries go from your browser to Cloudflare’s public DNS over HTTPS; nothing passes through our servers.
| IP address | Hostname (PTR) | Points back? |
|---|
What Reverse DNS Is
Ordinary DNS turns a name into an address: dns.google becomes 8.8.8.8. Reverse
DNS goes the other way. The address is written backwards under a special domain —
8.8.8.8.in-addr.arpa for IPv4, a long string of single hex digits under ip6.arpa for
IPv6 — and a PTR record there names the host.
The important part is who controls that record. It is not whoever owns the hostname; it is whoever holds the address block — your ISP, or the hosting company that rents you the server. That is why you set it in a hosting control panel or ask your provider, not in your domain’s DNS.
Why “Points Back” Matters
Anyone who controls an address block can make its PTR record say anything, including a name they don’t own. So a reverse lookup on its own proves little. The check that means something is the round trip: the PTR hostname must itself resolve back to the same IP address. This is called forward-confirmed reverse DNS, and it is what this tool tests in the third column.
For anyone running a mail server: Google’s rules for everyone sending to Gmail say the sending server’s public IP must have a PTR record, and that hostname must have an A or AAAA record that resolves to the same IP. A red or amber result in the third column for your mail server’s address is worth fixing before anything else in your email setup.
Reading the Result
| Result | What it means |
|---|---|
| Confirmed | The hostname resolves back to the same address. The setup a mail server expects. |
| Points elsewhere | The hostname exists but resolves to different addresses. Common on shared hosting; a problem for sending email. |
| No forward record | The PTR names a host that has no address at all. Usually a stale or placeholder record. |
| No PTR record | Nobody has set a reverse name. Normal for many cloud servers and some home connections — and a reason for mail servers to refuse email from it. |
What a Hostname Can Tell You
Reverse names are written by the network operator, so they often carry its name and sometimes more:
home broadband addresses frequently get long generated names containing words like dynamic,
pool or dsl, and some providers include a city or exchange code. None of that is
guaranteed — it is whatever the operator chose to write — but it is a quick way to see whether an address
belongs to a home connection, a business line or a server.
What This Can’t Tell You
- Which websites live on an address. That is a different search, often called a “reverse IP lookup”, and it relies on crawled databases rather than DNS. A PTR record names at most one host per entry.
- Who the person is. A hostname identifies the operator’s naming scheme, not a subscriber.
- Whether email will be delivered. Reverse DNS is one requirement among several. Check SPF, DKIM and DMARC and whether the address is on a blacklist too.
Want to know who runs the network behind an address?
ASN Lookup DNS Checker Email Header AnalyzerFrequently Asked Questions
How do I set reverse DNS for my server?
In your hosting or cloud provider’s control panel — it is usually listed next to the server’s IP address as “reverse DNS” or “PTR”. Set it to a hostname you control, then make sure that hostname has an A (or AAAA) record pointing back to the same address. Run this tool afterwards; it should show Confirmed.
Why does my home IP have no hostname, or a very long one?
Your ISP sets it, not you. Many give every customer address a generated name; some don’t bother. Either is normal for a home connection.
Why can’t I look up 192.168.x.x?
Private addresses only exist inside your own network, so public DNS has no reverse records for them. Your router may answer for them locally, but that never reaches the internet.
Can an address have more than one PTR record?
It can, though it is discouraged and some mail servers handle it badly. All of them are listed, and the result counts as confirmed if any one points back.