Look up the reverse DNS (PTR record) hostname for an IP address
• IP address: enter an IPv4 or IPv6 address
• Reverse-resolves the hostname associated with an IP via PTR record
• Some IP addresses may not have a PTR record configured
Reverse DNS lookup queries the PTR record in the reverse DNS zone (in-addr.arpa for IPv4, ip6.arpa for IPv6) for an IP address, resolving it to a hostname if one is configured. PTR records are set by the IP address owner — typically an ISP or cloud provider — and are used by many email servers and logging systems to associate hostnames with IP addresses.
Common uses include identifying the hostname associated with an IP in server logs or connection records, verifying that a mail server has a matching forward-confirmed reverse DNS (FCrDNS) record as required by many receiving servers, and auditing IP infrastructure to understand which hostnames are published for your address blocks.
PTR records are managed by the IP address owner, not the hostname owner. If your ISP or cloud provider has not configured reverse DNS for your IP block, the lookup returns nothing. Many cloud providers allow custom PTR records through their console.
FCrDNS means the PTR record for the IP resolves to a hostname, and that hostname's A record resolves back to the same IP. Many email servers require FCrDNS on the sending IP to reduce spam classification risk.
Not strictly, but PTR records are strongly recommended for mail servers. For general web or application servers they are optional, though having a meaningful PTR record improves transparency in log analysis and network audits.
Only the IP address owner can set PTR records. For IPs assigned by an ISP, you need to request a PTR record through them. For IPs from cloud providers, you can usually set it via the provider's console or API.