Reverse DNS (PTR) Lookup Generator
Generate reverse DNS (PTR) lookup commands for any IPv4 or IPv6 address or CIDR. Builds the exact in-addr.arpa / ip6.arpa reverse-zone query name, plus ready-to-paste dig / nslookup / kdig (DoH) / host commands against Google, Cloudflare, Quad9, OpenDNS, or a custom resolver. Parses PTR zone records, builds a forward-confirmed reverse DNS (FCrDNS) chain, flags private/loopback/link-local IPs, and generates batch scripts. 100% client-side — generates commands only; actual lookups require running them in your terminal.
About Reverse DNS (PTR) Lookup Generator
Generate reverse DNS (PTR) lookup commands for any IPv4 or IPv6 address or CIDR. Builds the exact in-addr.arpa / ip6.arpa reverse-zone query name, plus ready-to-paste dig / nslookup / kdig (DoH) / host commands against Google, Cloudflare, Quad9, OpenDNS, or a custom resolver. Parses PTR zone records, builds a forward-confirmed reverse DNS (FCrDNS) chain, flags private/loopback/link-local IPs, and generates batch scripts. 100% client-side — generates commands only; actual lookups require running them in your terminal. Everything runs locally in your browser — your data never leaves your device.
How to use
- Enter your input in the tool above.
- Adjust any options to your preference.
- Use the Copy or Download buttons to save the result.
- Everything happens locally — your data never leaves your browser.
FAQ
Does this tool perform live reverse DNS lookups?
No. Reverse DNS lookups require the network — and this tool is 100% client-side, so it generates the exact `dig -x`, `nslookup -type=PTR`, `kdig` (DoH), and `host` commands for you to copy and run in your terminal against your chosen resolver (Google 8.8.8.8, Cloudflare 1.1.1.1, Quad9 9.9.9.9, OpenDNS, or a custom IP/host). The reverse-zone name (in-addr.arpa / ip6.arpa) is constructed locally and works offline. PTR records are maintained by the IP owner/ISP, so many addresses legitimately have no PTR.
How is the in-addr.arpa / ip6.arpa name built?
For IPv4, the four octets are reversed and appended to `.in-addr.arpa` — e.g. `192.0.2.1` → `1.2.0.192.in-addr.arpa`. For IPv6, the address is first fully expanded to 32 hex nibbles, each nibble is reversed, and the result is appended to `.ip6.arpa` — e.g. `2001:db8::1` → `1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa`. The tool always shows the generated zone name alongside every command so you can verify the lookup target.
What is FCrDNS and how does this tool help with it?
FCrDNS (Forward-Confirmed Reverse DNS) is a two-step check mail servers run: (1) query the PTR for the IP → hostname; (2) query A/AAAA for that hostname → IP set; (3) verify the original IP is in that set. It is the PTR check that actually matters for email deliverability. The tool generates the full chain (PTR query + A/AAAA query for the returned hostname) so you can run both halves in your terminal and compare answers manually. When the chain fails, you get a deliverability explanation to share with the IP owner.
How are CIDR ranges handled?
Enter a CIDR like `192.0.2.0/30` and the tool enumerates every host IP in the range (capped at 256 to keep command output sane — `/24` for IPv4 and `/120` for IPv6 are the practical limits), then generates a PTR query per address. Larger CIDRs are rejected with a clear error message and a suggestion to narrow the range. Each generated address has its own reverse-zone name, dig/nslookup/kdig/host command, and copy button.
What extra features does this tool have versus other reverse DNS sites?
(1) Correct IPv4 in-addr.arpa construction. (2) Correct IPv6 ip6.arpa (nibble-reversed) construction with full expansion. (3) CIDR range enumeration with a 256-address cap. (4) FCrDNS chain builder (PTR + A/AAAA). (5) Private/loopback/link-local/reserved IP detection — flagged so you don't waste queries. (6) dig / nslookup / kdig (DoH) / host command variants. (7) 5 resolver presets (Google, Cloudflare, Quad9, OpenDNS, custom). (8) PTR zone-record parser (name TTL IN PTR target). (9) Batch .sh script generator for ranges. (10) Hostname → IP → PTR convenience chain. (11) Copy-to-clipboard per command. (12) localStorage history (max 20). (13) Shareable URL. 100% client-side — never sends queries itself.
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