--- title: "Reverse DNS Lookup" description: "Find the hostname behind an IPv4 or IPv6 address. Reads its PTR record through Google Public DNS or Cloudflare over HTTPS, and says plainly when there is none." url: https://findutils.com/network/reverse-dns-lookup/ category: network --- # Reverse DNS Lookup Find the hostname behind an IPv4 or IPv6 address. Reads its PTR record through Google Public DNS or Cloudflare over HTTPS, and says plainly when there is none. **Use this tool:** [Reverse DNS Lookup](https://findutils.com/network/reverse-dns-lookup/) ## Programmatic access - REST id `reverse-dns-lookup`: POST https://api.findutils.com/api/tools/reverse-dns-lookup/execute (reference: https://findutils.com/api/reverse-dns-lookup/) - MCP tool `reverse_dns_lookup` on https://mcp.findutils.com (reference: https://findutils.com/mcp/reverse-dns-lookup/) - Data: The REST API and the MCP tool are a separate path from this page: a call sends the input you include to FindUtils over HTTPS, where it is processed and the result returned. FindUtils does not store that input, and logs the request without its content. ## Why use a reverse DNS lookup? A forward lookup turns a name into an address. A reverse lookup asks the opposite question: which name does the owner of this address publish for it? Mail administrators check it before they send from a new server, because many receiving mail servers look at the PTR record of the connecting address. Abuse desks and anyone reading server logs use it to see whose network an address belongs to. This tool builds the reverse name correctly for both IPv4 and IPv6, asks a public resolver over HTTPS, and tells you plainly when there is no PTR record. ## Tips for Reverse DNS - A PTR record is set by whoever controls the address block, so ask your hosting or cloud provider, not your domain registrar. - Check the result both ways: the PTR name should resolve back to the same address with a forward A or AAAA lookup. - Try both resolvers after a change. Each one keeps its cached answer until its TTL runs out. - An address can have more than one PTR record, but mail servers expect one. Keep a single, specific name for a mail server's address. - NXDOMAIN for a home or cloud address is common and not an error; it only means nobody published a name. ## Frequently Asked Questions ### What is a reverse DNS lookup? A reverse DNS lookup finds the hostname published for an IP address. It reads the address's PTR (pointer) record, which lives under a special name built from the address: 8.8.8.8 is looked up as 8.8.8.8.in-addr.arpa, and the PTR record there says dns.google. It is the opposite of a normal DNS lookup, which turns a hostname into an address. ### How is the PTR name built for an IPv6 address? The IPv6 address is first written out in full, as 32 hexadecimal digits with every zero restored, then the digits are reversed and separated by dots under ip6.arpa. For 2001:4860:4860::8888 the name is 8.8.8.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.6.8.4.0.6.8.4.1.0.0.2.ip6.arpa. This tool accepts the short form with :: and builds that name for you, so you do not have to count zeros. ### What does "No PTR record" or NXDOMAIN mean? It means nobody has published a hostname for that address. NXDOMAIN is the response code for a name that does not exist, so the reverse name for the address was never created. A NOERROR answer with no records means the reverse name exists but holds no PTR record. Both are normal for many addresses, especially home connections and cloud addresses whose owner never set a name. ### Who sets the PTR record for an IP address? The organisation that controls the address block sets it: usually your hosting provider, cloud provider or internet service provider, not your domain registrar. Your own DNS zone cannot change it. To set or change a PTR record, use your provider's control panel or ask its support, then check the result here. ### Why does reverse DNS matter for email? Many receiving mail servers check the PTR record of the address that connects to them, and some compare it with the forward record of that hostname. A sending server with no PTR record, or with a generic one, is more likely to have its mail rejected or filtered as spam. Before you send mail from a new server, check that its address has a PTR record naming your mail host. ### Can I look up a private address like 10.0.0.1 or 192.168.1.1? You can, but a public resolver cannot tell you its name. Private, loopback and link-local addresses are only meaningful inside one network, so a public resolver answers NXDOMAIN for them. To find the name of a device on your own network, ask your router or the DNS server inside that network. ### Why do Google Public DNS and Cloudflare show different TTLs? The TTL is the number of seconds a resolver may keep its cached copy of the answer, and it counts down from the moment that resolver fetched the record. Two resolvers that fetched the record at different times show different remaining TTLs for the same PTR record. The hostname itself is the same unless the record changed recently. ### Does a PTR record prove who owns an address? No. Whoever controls the reverse zone can publish any name, including a name in a domain they do not own. A PTR record is more trustworthy when the hostname it names resolves back to the same address, which is called forward-confirmed reverse DNS. Use the [DNS Lookup](https://findutils.com/network/dns-lookup/) to check the A or AAAA record of the hostname you found, and the [WHOIS Lookup](https://findutils.com/network/whois-lookup/) to read registration data. ### Is the IP address I look up private? On this page, the IP address is sent from your browser straight to the resolver you pick, Google Public DNS (dns.google) or Cloudflare (cloudflare-dns.com), over HTTPS. It does not pass through FindUtils, and FindUtils keeps no record of it. The REST API and MCP tool are a separate path: a call sends the input you include to FindUtils over HTTPS, where it is processed and the result returned. FindUtils does not store that input, and logs the request without its content. ## Related Tools - [IP Address Lookup](https://findutils.com/network/ip-address-lookup/) - [DNS Lookup](https://findutils.com/network/dns-lookup/) - [DNS Propagation Checker](https://findutils.com/network/dns-propagation-checker/) - [WHOIS Lookup](https://findutils.com/network/whois-lookup/) - [IP Blacklist Checker](https://findutils.com/network/ip-blacklist-checker/) - [Email Header Analyzer](https://findutils.com/network/email-header-analyzer/) - [DNS Security Scanner](https://findutils.com/network/dns-security-scanner/)