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Reverse DNS Lookup – Find the Host Name of an IP Address

Find the host name behind an IP address from its PTR record, for one address or a whole list.

About Reverse DNS Lookup

A reverse DNS lookup turns an IP address back into a host name. Mail admins check it because many receiving servers distrust mail from an IP whose PTR record is missing or doesn't match, and webmasters use it to see which network an address in the access logs belongs to. To test whether a visitor claiming to be Googlebot or Baiduspider is real, Verify Googlebot and Baiduspider IPs runs the full check. Paste one address or a list, IPv4 or IPv6: up to 10 per check without an account, 20 for free members and 100 with VIP.

For each IP you get the PTR host name and whether it's forward-confirmed, meaning the name resolves back to the same IP, which is what mail servers look for. Addresses without a PTR record are marked No record. Click an address to open its IP WHOIS record, or a host name to run a DNS lookup on it. The table can be copied or saved as CSV. Lookups go through public DNS when you click, and nothing is stored.

How to use Reverse DNS Lookup

  1. 1
    Paste the IP addresses

    Enter one IPv4 or IPv6 address, or a list with one per line.

  2. 2
    Click Look up

    All the addresses are looked up at the same time through public DNS.

  3. 3
    Check the results

    Read the PTR host name and the Forward-confirmed column for each IP.

  4. 4
    Export or dig deeper

    Copy the table or save it as CSV, or click an IP to see who owns it.

Why use Cubfile for this

  • IPv4 and IPv6

    Both kinds of address work, even mixed in the same list.

  • Forward confirmation

    Checks that the PTR name points back to the same IP, as mail servers expect.

  • Bulk lookup

    Up to 10 addresses per check, 20 as a free member and 100 with VIP.

  • Linked results

    IP addresses open IP WHOIS, and host names open DNS Lookup.

FAQ

Reverse DNS Lookup: questions and answers

What is a PTR record in a reverse DNS lookup?
A DNS record that maps an IP address to a host name, the reverse of an A record. It's managed by whoever holds the IP block, usually your hosting provider or ISP.
How do I set up reverse DNS for my mail server?
Ask the provider that gave you the IP, because they control its PTR record, and many cloud panels have a setting for it. Point it at a host name that resolves back to the same IP.
What does forward-confirmed mean?
The PTR host name resolves back to the original IP. Mail servers and crawler checks rely on this, because anyone can put any name in the PTR record of their own IP.
Why does an IP have no PTR record?
Many addresses, especially home connections and new cloud servers, simply have none. That's fine for a website, but a mail server should have one.
How many IPs can I look up at once?
Up to 10 per check without an account, 20 as a free member and 100 with VIP. Lookups don't use your daily tasks.
Share Reverse DNS Lookup with a friendIt runs in any browser, and they can try it without signing up.

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