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PTR Record

Also known as: Pointer record, PTR, Reverse DNS record

A DNS record that maps an IP address back to a host name, the reverse of an A or AAAA record. It lives in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone and is set by whoever controls the address block.

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What is a PTR record?

A PTR record (pointer record) is the DNS record that answers the question "which name belongs to this IP address?". It is the reverse of an A record, which maps a name to an IPv4 address, and of an AAAA record, which does the same for IPv6. Looking up a PTR record is what a reverse DNS lookup does.

Here are two real PTR records, returned by dig -x on 12 November 2026:

dig -x 8.8.8.8 +noall +answer
8.8.8.8.in-addr.arpa.	75544	IN	PTR	dns.google.

dig -x 1.1.1.1 +noall +answer
1.1.1.1.in-addr.arpa.	1437	IN	PTR	one.one.one.one.

The number in the middle is the TTL, how many seconds a resolver may cache the answer. The PTR type is defined with the other basic record types in RFC 1035, the 1987 DNS specification.

How the reverse zone works

DNS is built to look names up, not numbers, so reverse lookups use a trick. The address is turned into a name in a special zone. For IPv4, the four numbers are written backwards under in-addr.arpa, so 203.0.113.25 becomes 25.113.0.203.in-addr.arpa. Backwards, because DNS names get more specific from right to left while IP addresses get more specific from left to right. For IPv6, each hexadecimal digit of the full address becomes its own label, reversed, under ip6.arpa, which gives a name 32 labels long.

The regional internet registry delegates the reverse zone for an address block to the organisation the block was assigned to. That is the key practical fact about PTR records: the record belongs to whoever controls the IP address, not to whoever owns the domain name. You set the A record for mail.example.com at your DNS host; the PTR for the server's address is set by the hosting company or internet provider that gave you the address.

Why mail servers check PTR records

The main use of PTR records today is in email. When a server connects to send mail, the receiving server looks up the PTR record of the connecting address, then looks up the A record of the name it gets back. If the name points back to the same address, the server has forward-confirmed reverse DNS (FCrDNS). Missing records and generic provider names (such as host-203-0-113-25.example-isp.net) are common in spam sent from infected home computers, so large mail providers treat them as a warning sign. Google's sender guidelines require senders to have valid forward and reverse DNS records for their sending addresses.

That is why anyone running a mail server has to ask their host for a PTR record that matches the server's name, and why it pairs with the domain's MX record, SPF and DKIM. The SMTP conversation itself does not need it; deliverability does.

What a PTR record tells you about an address

On someone else's address, the PTR name is often the quickest clue to what it is. A name like dns.google identifies a service. Names that contain the address and words such as dsl, cable, pool or dynamic usually mean a home connection, and names with cloud, compute or a hosting brand mean a server. None of this is guaranteed, since the owner can write anything in the record, but it is a useful first look. Our reverse DNS lookup shows the PTR of any address, and the email header analyzer shows the host names of the servers a message passed through.

Frequently Asked Questions

Mostly for email and for reading logs. Receiving mail servers look up the PTR record of the server that connects to them, and many reject or downgrade mail from an address with no PTR or one that does not match. Network tools and log viewers use PTR records to show a host name instead of a bare address, which often reveals the provider and the type of connection.
If you run a mail server, yes: without one, many large mail providers will reject or spam-folder your mail. For a website, a VPN server or a home connection, no; nothing breaks without one. Your provider usually sets a generic one for its addresses anyway.
Ask whoever controls the IP address, because the record lives in their reverse zone, not in your domain's DNS. Cloud and VPS providers usually offer a reverse DNS or PTR field in the server's network settings. On a business connection, your internet provider sets it on request. You cannot add one at your domain registrar.
An A record maps a name to an IPv4 address and sits in your domain's zone, which you control. A PTR record maps an address back to a name and sits in the reverse zone of the address block, which its owner controls. The two are independent: one can exist without the other, which is why mail servers check that they match.
DNS allows it, but it is a bad idea. Software that does a reverse lookup usually takes the first answer, so which name you get becomes unpredictable, and mail checks may fail. One address, one PTR, matching a name whose A record points back to the same address, is the setup to aim for.
Run dig -x followed by the address on macOS or Linux, or nslookup followed by the address on Windows. Our reverse DNS lookup does the same in a browser. If there is no record, the answer is NXDOMAIN or an empty result, which is common for home and mobile addresses.
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