Reverse DNS Lookup

Resolve any IPv4 or IPv6 address to its hostname via PTR record. Verify rDNS setup, confirm forward-confirmed reverse DNS (FCrDNS), and diagnose email deliverability issues in real time — no sign-up needed.

Enter any IPv4 or IPv6 address to retrieve its PTR record, hostname and forward-confirmation status.
Enter an IP address to look up its PTR record
Type any IPv4 or IPv6 address above to retrieve its hostname via reverse DNS, check forward-confirmation status and view network details.
Not stored or logged
Real-time PTR lookup
No sign-up needed

What This Tool Does

This tool performs a live reverse DNS lookup against the authoritative DNS zone for any IPv4 or IPv6 address. It queries the in-addr.arpa zone for IPv4 or ip6.arpa for IPv6, retrieves any PTR records configured there, and then runs a forward-confirmation check — querying the returned hostname in standard DNS to verify it resolves back to the original IP address.

PTR Record Lookup

Queries the correct ARPA zone for any IPv4 or IPv6 address and returns all PTR records configured by the IP block owner.

FCrDNS Verification

Runs a forward-confirmation check on each PTR hostname to verify it resolves back to the original IP, as required by mail servers.

Provider Classification

Identifies the provider behind the hostname — AWS, Google, Hetzner, Cloudflare, residential ISP, mail server, and more.

Network & ISP Details

Retrieves the ISP, organisation, AS number and AS name for any IP alongside the PTR data for a complete network profile.

Diagnosing Common Reverse DNS Problems

Frequently Asked Questions

What is reverse DNS and how does it work?

A standard (forward) DNS lookup translates a domain name into an IP address — for example resolving example.com to 93.184.216.34. Reverse DNS does the inverse: given an IP address, it returns the hostname configured for it via a PTR record. The lookup queries a special DNS zone called in-addr.arpa for IPv4, where the four octets of the IP are reversed and used as the query name. For 8.8.8.8 this becomes 8.8.8.8.in-addr.arpa. For IPv6, the equivalent zone is ip6.arpa, where all 128 bits are expanded to nibbles, reversed and dot-separated.

This tool performs the full lookup including both the PTR query and a forward-confirmation step that verifies the returned hostname actually resolves back to the original IP. The ARPA query name used for each lookup is shown below the results so you can verify or reproduce it manually. To look up forward DNS records for any domain name, use our DNS Lookup tool.

What is a PTR record and who controls it?

A PTR (pointer) record is the DNS record type used exclusively for reverse lookups. Unlike A or CNAME records which you manage through your domain registrar, PTR records are controlled by whoever holds the IP address block — typically your ISP for home broadband connections, or your hosting provider for cloud and dedicated servers. This is because PTR records live in zones delegated alongside IP address block allocations from IANA through the regional registries (ARIN, RIPE, APNIC etc.).

For example, the PTR record for 8.8.8.8 is managed by Google and points to dns.google. Google controls this because they own the IP block. You cannot configure PTR records through Cloudflare, Namecheap, GoDaddy or any other domain registrar — only through the entity that assigned you the IP address. Use our WHOIS Lookup to identify who controls any IP block and find the correct contact for requesting a PTR record.

What is FCrDNS and why does it matter for email?

Forward-Confirmed Reverse DNS (FCrDNS) is a two-step verification. Step one: a reverse DNS lookup resolves the sending IP to a hostname via its PTR record. Step two: that hostname is queried in standard forward DNS to check whether it resolves back to the original IP. If both steps produce a match, the PTR is forward-confirmed — the hostname and IP agree from both directions.

Gmail, Outlook, Yahoo Mail, and virtually all enterprise spam filters check FCrDNS on every incoming SMTP connection. Mail from servers with valid FCrDNS is trusted significantly more than mail from servers without it. A missing PTR causes an automatic FCrDNS failure. A PTR that exists but whose hostname does not resolve back to the original IP also fails — this is common when a PTR record is set to a hostname but the matching A record is never created. Verify your forward DNS A record with our DNS Lookup and check your SPF, DKIM and DMARC TXT records there too for a complete email deliverability picture.

Why does my IP have no PTR record?

PTR records must be explicitly configured by whoever controls the IP block — they are not created automatically when an IP is assigned. Residential broadband connections almost never include a PTR record because there is no operational reason for one at that scale. Many cloud and VPS providers ship new server instances without a PTR record until you configure it manually in the provider's control panel or request one via support.

A missing PTR is entirely normal for the vast majority of IPs on the internet and only becomes a problem in specific contexts — most importantly when running an outbound email server, where receiving mail servers use PTR records as a spam signal. For any other use case, no PTR is not an error. If you need to set one up for a mail server, the process depends on your provider: DigitalOcean, Hetzner and Vultr allow custom PTR records directly in their control panels; AWS requires configuration through Route 53 or a support request; residential ISPs typically require a support ticket.

How do I set up a PTR record for my mail server?

PTR records are configured through whoever assigned you the IP address, not your domain registrar. For most cloud providers — DigitalOcean, Hetzner, Vultr, Linode — you can set the PTR directly in the server or networking section of the control panel. For AWS EC2, you configure it through the Elastic IPs section or by opening a support ticket. For dedicated or co-located servers it typically requires a support ticket to your upstream ISP or hosting provider.

The PTR hostname you set should match the hostname your mail server announces in its SMTP EHLO greeting, and that hostname must have an A or AAAA record pointing back to the server IP. After setting it up: verify the A record with our DNS Lookup, confirm the PTR resolves correctly here, check mail ports are open with our Port Checker (25, 587, 465), and verify the TLS certificate with our SSL Checker. Give DNS changes up to 48 hours to propagate fully before testing deliverability.

What is the in-addr.arpa zone?

The in-addr.arpa zone is the special DNS zone used for IPv4 reverse lookups. To query the PTR record for any IPv4 address, DNS reverses the four octets and appends .in-addr.arpa — so 192.0.2.1 becomes 1.2.0.192.in-addr.arpa. The reversal exists because DNS delegation flows left-to-right from general to specific (like a domain name), while IP addresses read from most to least significant octet (the opposite direction). By reversing the IP, DNS delegation for IP blocks works the same way as domain delegation.

IPv6 uses the ip6.arpa zone where the 128-bit address is expanded into 32 hexadecimal nibbles, reversed, and dot-separated — producing a much longer query name. This tool shows the exact ARPA query name used for every lookup in the strip below the result cards, so you can verify or reproduce it manually using dig or nslookup.

Can one IP address have multiple PTR records?

Technically yes — the DNS standard does not prohibit multiple PTR records per IP, and this tool retrieves and displays all of them when multiple exist. However, multiple PTR records per IP are rare in practice and generally discouraged. Most mail servers, spam filters and network diagnostic tools expect exactly one PTR record per IP, and some filtering systems treat multiple PTR records as an anomalous signal that may reduce trust scores.

When multiple PTR records are found, this tool runs an independent forward-confirmation (FCrDNS) check against each hostname separately and shows the individual results in the detail panel. If you see unexpected PTR entries for an IP you control, use our WHOIS Lookup to confirm the block ownership, then contact the IP block owner to investigate and remove any incorrect records.

What is the difference between reverse DNS and WHOIS?

Reverse DNS queries the DNS system for the hostname linked to an IP address via its PTR record — it answers the question "what hostname does this IP announce?" A WHOIS lookup queries a separate registration database maintained by regional internet registries for administrative details about an IP block — including the owner, organisation, contact information, and network allocation boundaries.

Together they provide complementary information: reverse DNS tells you the hostname the IP owner has chosen to publish, while WHOIS tells you who actually owns and is responsible for the IP block. Both are needed for a complete picture. If an IP shows no PTR record here, WHOIS will tell you who to contact to request one. If a PTR hostname looks suspicious, WHOIS on the IP block can confirm or contradict what the PTR claims about its origin.

Is this tool storing my query data?

No. Every result is fetched live at the moment you submit the form — the PTR lookup, the forward-confirmation DNS queries, and the geolocation data are all retrieved in real time and not cached on Convixy's servers. There is no query logging associated with individual IP lookups and no data retention beyond the duration of the server-side DNS calls. No account is required to use the tool, so there is no user profile for queries to be linked to.

Standard web server access logs record the URL of each page request — which includes the IP you looked up as a query parameter — for security and uptime monitoring purposes. These logs are periodically rotated and are not used for tracking or profiling. For a complete network investigation, combine this with our What Is My IP, DNS Lookup, WHOIS Lookup and Port Checker — all free and real-time with no sign-up.