Reverse DNS Lookup

Look up the hostname registered for an IPv4 address. The tool builds the special in-addr.arpa domain from your address, queries its PTR record, and shows every hostname that comes back, which is what mail servers do when they check whether a sending IP looks legitimate.

IPv4 Address

How was this tool?

Your feedback helps us improve Reverse DNS Lookup.

Why use Reverse DNS Lookup?

Forward DNS answers what address a name points to. Reverse DNS answers the opposite question, and it is not simply the same data read backwards. It lives in its own zone, controlled by whoever was allocated the address block, which is why you can point a domain at any IP you like but cannot set the reverse entry without your provider. The mechanism is a small piece of cleverness. The address parts are reversed and in-addr.arpa is appended, turning the lookup into an ordinary domain query. Reversing matters because domain names get more specific from right to left while IP addresses get more specific from left to right, so flipping them lets address blocks be delegated the same way subdomains are. Where this bites in practice is email. Most receiving mail servers check the connecting address for a PTR record, and many go further and confirm that the hostname resolves back to the same address. Missing or mismatched reverse DNS is one of the most common causes of legitimate mail being rejected, which is why it is worth checking before blaming your message content.

Key benefits

Validates the address before querying, so a typo is caught immediately
Handles the in-addr.arpa construction for you rather than expecting you to reverse the octets
Distinguishes no record found from a lookup that failed
Shows every PTR record when an address has several
Query runs server side, so no DNS client is needed on your machine

Features

IPv4 validation covering both part count and the 0 to 255 range
Automatic reversal of the octets into the in-addr.arpa form
PTR record query through the site's DNS endpoint
Explicit empty result state
Enter key submits the form

Popular use cases

Checking whether a mail server IP has the reverse record delivery requires
Identifying the network behind an address in a server log
Confirming reverse DNS after a hosting provider sets it up for you
Investigating an unfamiliar address that appeared in an access log

How to use Reverse DNS Lookup

1
Enter an IPv4 address
Type the address in dotted form, for example 8.8.8.8. Each of the four parts is validated before the query is sent.
2
Run the lookup
The address is reversed and turned into an in-addr.arpa domain, and its PTR record is queried.
3
Read the hostnames
Any PTR records found are listed. An address can legitimately have more than one.
4
Check the empty case
No record is a real answer rather than an error. Plenty of addresses have no reverse entry configured.

Frequently asked questions

What is a PTR record?

It is the reverse of an A record. An A record maps a name to an address, and a PTR record maps an address back to a name. It lives in a special zone: the address has its four parts reversed and in-addr.arpa appended, so 8.8.8.8 is looked up as 8.8.8.8.in-addr.arpa.

Why does reverse DNS matter for email?

Receiving mail servers routinely check whether the connecting IP has a PTR record, and often whether that hostname resolves back to the same address. An address with no reverse entry is a common reason for outbound mail being rejected or filed as spam.

Why does my address have no PTR record?

Because reverse DNS is controlled by whoever owns the address block, not by you. Home broadband addresses usually carry a generic hostname assigned by the provider, and many hosting addresses have none until you ask for one to be set.

Can one address return several hostnames?

Yes, and it is valid. A server hosting multiple services may have more than one PTR record, so all results are listed rather than only the first.

Does this work for IPv6?

Not in this version. IPv6 reverse lookups use the ip6.arpa zone with a different and considerably longer nibble format. Only IPv4 addresses are accepted here.

Last reviewed: July 2026

How was this tool?

Related tools