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Reverse DNS lookup

Find the hostname behind any IP address. Enter an IPv4 or IPv6 address and we'll fetch its PTR record, verify it resolves back to the same IP, and show you who operates the network.
For example, try 8.8.8.8 or 1.1.1.1.

What is a reverse DNS lookup?

A reverse DNS lookup (rDNS) finds the domain name associated with an IP address — the opposite of a normal DNS query, which turns a name into an IP. It works by querying the IP's PTR record in the special in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone. Reverse DNS is most often used to verify mail servers, make server logs readable, and identify who is behind a connection.

Not every IP address has a PTR record. Reverse DNS is configured by whoever controls the IP range — usually a hosting provider, ISP, or cloud platform — not by the domain owner. That's why setting it up works differently from normal DNS records (see "How to set up a PTR record" below).

How to use this tool

  1. Enter an IP address — IPv4 like 8.8.8.8 or IPv6 like 2001:4860:4860::8888.
  2. Select "Find hostname". We query the address's PTR record from the authoritative servers for its reverse zone.
  3. Read the result. You'll see the hostname, its TTL, whether the hostname resolves back to the same IP (forward-confirmed reverse DNS), and the network that announces the address. Select the hostname to see all of its DNS records.

What is a PTR record?

A PTR (pointer) record is the DNS record type that stores a reverse mapping: it points an IP address back to a hostname. For the IPv4 address 8.8.8.8, the PTR record lives at 8.8.8.8.in-addr.arpa (the octets reversed) and its value is dns.google. IPv6 addresses use the ip6.arpa zone, with each hex digit reversed and dot-separated.

PTR records are the mirror image of A and AAAA records — but they live in a different zone, controlled by the owner of the IP block rather than the owner of the domain. One IP can have multiple PTR records, though a single record is strongly recommended for mail servers. Read more in our PTR record guide.

Why reverse DNS matters

  • Email deliverability: most mail servers check that a sending server's IP has a PTR record and that it forward-confirms. Missing or generic reverse DNS is one of the most common reasons legitimate email lands in spam. Gmail, Outlook and Yahoo all check it.
  • Readable logs: web-server and firewall logs record IPs; reverse DNS turns 66.249.66.1 into crawl-66-249-66-1.googlebot.com so you can see at a glance who's hitting your servers.
  • Bot verification: verifying that a client claiming to be Googlebot, Bingbot or another crawler really is one: do a reverse lookup on its IP, then confirm the hostname resolves back to the same IP. Both checks must pass.
  • Diagnostics: network troubleshooting tools like traceroute display reverse names for each hop, revealing the networks a route passes through.

How to do a reverse DNS lookup from the command line

You can run a reverse DNS lookup from any terminal. All three commands below query the PTR record for 8.8.8.8: 

nslookup 8.8.8.8
dig -x 8.8.8.8 +short
host 8.8.8.8

nslookup automatically detects that the input is an IP address and performs a PTR query. dig requires the -x flag, which converts the address to in-addr.arpa notation for you; +short prints only the hostname. All three work for IPv6 addresses too — no special syntax needed.

What is forward-confirmed reverse DNS (FCrDNS)?

Forward-confirmed reverse DNS means the PTR record and the forward record agree: the IP resolves to a hostname, and that hostname resolves back to the same IP. Mail providers treat FCrDNS as a baseline authenticity check because both the IP-block owner and the domain owner must cooperate to fake it. This tool runs the confirmation automatically and shows the result next to every lookup.

How to set up or fix a PTR record

PTR records are managed by whoever controls the IP address, so where you set one up depends on where your server runs:

  • Cloud providers: AWS, Google Cloud, Azure, DigitalOcean, Hetzner and most others let you set the PTR record in their console or via a support form — look for "reverse DNS" or "PTR" in the instance's network settings.
  • Hosting/ISP: for a dedicated server or colocation, ask your provider to set the PTR, or — for larger allocations — have the reverse zone delegated to your own name servers.
  • Mail servers: set the PTR to your mail server's HELO/EHLO hostname (e.g. mail.example.com), make sure that hostname has a matching A/AAAA record, and use exactly one PTR record per IP.

After changing a PTR record, use this tool to confirm the new value, and our DNS propagation checker to watch it spread to resolvers worldwide.

Frequently asked questions

Why does my IP have no PTR record?

PTR records are optional and must be created by the owner of the IP range. Residential and mobile IPs often have generic or missing reverse DNS. If it's your server's IP, set the PTR in your hosting provider's control panel or ask their support.

Can one IP address have multiple hostnames?

Yes — an IP can technically hold several PTR records, and this tool shows all of them. For mail servers, use exactly one: multiple PTR records confuse spam filters and some will treat the setup as misconfigured.

Is reverse DNS the same as a WHOIS lookup?

No. Reverse DNS returns the hostname configured in the IP’s PTR record. WHOIS returns registration data about who was allocated the IP range. They answer different questions and are often used together.

Does reverse DNS reveal all websites hosted on an IP?

No. A PTR record holds the name the IP owner chose — typically one canonical hostname. On shared hosting, hundreds of sites can share an IP that reverse-resolves to a single provider hostname.

How long does a PTR record change take to propagate?

The same rules as any DNS record: until the old record's TTL expires everywhere, typically minutes to 48 hours. Use our DNS propagation checker to watch it update across the world.

Do I need reverse DNS if I don't run a mail server?

It's not required, but it's good hygiene: it makes your server identifiable in other people's logs and traceroutes, and some services rate-limit or block IPs with no reverse DNS.

Related tools

Know when your reverse DNS breaks

A silently deleted PTR record can put your email in spam for weeks before anyone notices. We'll monitor your PTR records and email you the moment one changes or disappears. Free for your first IP.

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