---
title: "Reverse DNS lookup"
description: "Look up the reverse DNS (PTR record) of any IPv4 or IPv6 address for free, and check that its hostname points back to the same IP. No sign-up."
canonical: https://www.acquisity.ai/tools/reverse-dns-lookup
---

# Reverse DNS lookup

> Look up the reverse DNS (PTR record) of any IPv4 or IPv6 address for free, and check that its hostname points back to the same IP. No sign-up.

Type an IPv4 or IPv6 address. We find its PTR record and check that the hostname points back to the same address, as email servers expect.

Use the tool in a browser at [/tools/reverse-dns-lookup](https://www.acquisity.ai/tools/reverse-dns-lookup). It is free and needs no sign-up.

## What reverse DNS is

Normal DNS turns a name into an IP address. Reverse DNS goes the other way: it turns an IP address into a hostname, using a PTR record stored under a special name with the address written backwards, such as 25.2.0.192.in-addr.arpa for 192.0.2.25. IPv6 addresses work the same way under ip6.arpa.

Whoever controls the IP address sets its PTR record. That is usually the hosting provider or internet provider, not the company that runs your domain’s DNS.

## Why it matters for email

Gmail’s sender guidelines ask every server that sends email to Gmail to have a PTR record, and the hostname in it must have an [A record](https://www.acquisity.ai/tools/a-record-lookup) (for IPv4) or an AAAA record (for IPv6) that points back to the same IP address. Google says email from senders that don’t meet its requirements might not be delivered as expected, or might be marked as spam.

Email services such as Google Workspace and Microsoft 365 set up reverse DNS for their own servers. For a mail server you run, ask whoever gave you its IP address, usually your hosting provider, to set it.

## Questions

### How do I do a reverse DNS lookup?

Type the IP address and press Look up. We ask DNS for its PTR record, then look up the hostname we find to check that it points back to the same address.

### Why does my IP address have no reverse DNS?

Many addresses have none, because nobody set one up. Ask whoever gave you the address, usually your hosting provider, to add a PTR record for it. Private addresses such as 192.168.1.1 and 10.0.0.1 are used only inside a network, so they never have public reverse DNS, and we say so without looking them up.

### Can I look up a range of addresses?

No, one address at a time. Type a single address such as 8.8.8.8, without a port or a range like /24.

### What does “points back” mean?

It means the hostname in the PTR record has an A record (for IPv4) or AAAA record (for IPv6) with the same IP address. This match is also called forward-confirmed reverse DNS.

## Sending cold email? Keep it off your main domain.

Acquisity sends cold email from separate domains, with SPF, DKIM and DMARC set up for you. [Cold Email Agent](https://www.acquisity.ai/agents/cold-email).

---

Web page: https://www.acquisity.ai/tools/reverse-dns-lookup
Site index for agents: https://www.acquisity.ai/llms.txt