Reverse DNS Lookup
This free reverse DNS lookup finds the PTR record for an IP address, the hostname it maps back to. Paste up to 20 IPv4 or IPv6 addresses, or one hostname, and it also checks that each name resolves back to the same IP, which is what mail servers look for.
The check runs in your browser, so we never see what you type and nothing is stored. Your browser asks Cloudflare (cloudflare-dns.com) for the DNS answers and falls back to Google (dns.google) if Cloudflare doesn't answer, so those two services can see the addresses and names you look up.
Free, no signup.
What a reverse DNS lookup shows
A normal DNS lookup turns a name into an address. Reverse DNS goes the other way: it asks which name belongs to an IP address. The answer is stored in a PTR record, in a special zone under in-addr.arpa for IPv4 and ip6.arpa for IPv6.
The table shows one row per address: the PTR name, a forward-confirmed check, and a short note. Addresses without a PTR record are marked, and private addresses such as 192.168.1.10 are listed as not checked because they only exist inside a home or office network.
What forward-confirmed means
Anyone who controls the reverse zone for an address can put any name in its PTR record, so a PTR name alone proves very little. The forward-confirmed check (often called FCrDNS) looks up the address of that name and checks that it includes the IP you started from.
If it does, the row passes. If the name points somewhere else, the row shows a warning that the PTR name doesn't point back to the IP. If an address has several PTR names, the row is marked as informational and lists how many of them were confirmed.
Who sets reverse DNS, and why mail servers care
Reverse DNS is set by whoever owns the block of IP addresses, which is usually your hosting provider or internet provider, not the owner of the domain. You normally ask them to set it, or change it in their control panel if they offer that.
Many mail servers look up the PTR record of the server that is sending to them, and then check that the name points back to that IP. A missing or mismatched record is a common reason that legitimate mail is rejected or sent to spam. For a mail server, the PTR name should match the name it uses to introduce itself.
How the lookup works in your browser
Your browser asks Cloudflare (cloudflare-dns.com) over DNS over HTTPS, and falls back to Google (dns.google) if Cloudflare does not answer. We don't receive the addresses you enter. Up to four addresses are checked at a time, and results appear as they arrive.
If you enter a hostname instead, the page first finds its IPv4 and IPv6 addresses and then checks the reverse DNS of each one. Up to five PTR names per address are checked.
Frequently asked questions
What is reverse DNS?
Reverse DNS finds the hostname that belongs to an IP address. It is the opposite of a normal lookup, which finds the address for a name. The answer is stored in a PTR record that the owner of the IP block publishes.
What is a PTR record?
A PTR (pointer) record maps an IP address to a hostname. For 203.0.113.5 it lives at 5.113.0.203.in-addr.arpa. IPv6 addresses use the same idea under ip6.arpa, with one label per hex digit.
What does forward-confirmed reverse DNS mean?
It means the name in the PTR record also resolves back to the same IP address. The check closes the loop: IP to name, then name to IP. Mail servers and other services use it as a basic sign that an address is set up properly.
Why does my IP have no reverse DNS?
Reverse DNS is not set up automatically. The owner of the IP block, usually your hosting or internet provider, has to add the PTR record. Ask them to set it, or look for a reverse DNS setting in their control panel.
Why do mail servers check reverse DNS?
Spam often comes from addresses with no PTR record or a name that doesn't match. Many mail servers therefore check that the sending IP has a PTR name that resolves back to it. A missing record can get your mail rejected or filed as spam.
Why does an address have more than one PTR name?
DNS allows several PTR records on one address, which happens on servers that host many sites. Most services only look at one of them, so one clear name that matches your mail server is the safer setup. The row shows how many names were confirmed.
Can I look up private addresses like 192.168.1.1?
Not on the public internet. Addresses such as 10.x.x.x, 172.16.x.x and 192.168.x.x are used inside home and office networks, so there is nothing to look up. The row says what kind of address it is.
Do you store the addresses I check?
No. The check runs in your browser and we don't receive what you enter. Your browser asks Cloudflare (cloudflare-dns.com), or Google (dns.google) as a fallback, for the DNS answers, so those services can see the lookups.
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