Reverse IP Lookup - Free Online PTR Record Checker
Resolve reverse DNS (PTR) for any public IPv4 address in seconds. Verify mail servers, confirm crawler identity, make server logs readable, and debug DNS configuration - free, with no signup required.
Look up PTR record
This tool performs a DNS PTR query via Google Public DNS. It returns the reverse hostname for an IP when a PTR record exists. It does not claim to enumerate every website sharing a shared-hosting IP (that requires a commercial co-location database).
Live PTR Queries
Resolved via Google Public DNS
Mail Deliverability
Same check receiving mail servers run
Crawler Verification
Confirm Googlebot, Bingbot & others
No Install Needed
Same result as dig -x or nslookup
What Is a Reverse IP Lookup (PTR Record) Tool?
A reverse DNS lookup (also called an rDNS lookup or PTR lookup) finds the hostname associated with an IP address - the exact opposite of a normal DNS query, which turns a domain name into an IP address. Where a forward lookup answers "what IP does example.com point to?", a reverse lookup answers "what hostname does this IP point back to?"
It works by querying a special reverse DNS zone called in-addr.arpa for IPv4 addresses (or ip6.arpa for IPv6). The IP address's octets are reversed and appended to that zone - for example, 8.8.8.8 becomes 8.8.8.8.in-addr.arpa - and a PTR (Pointer) record lookup against that name returns the hostname, if one has been configured for that IP.
This tool builds that reverse-zone query automatically and resolves it against Google Public DNS, giving you the same result as running dig -x or nslookup in a terminal, without needing command-line access.
Forward DNS vs. Reverse DNS
Forward DNS (A / AAAA records)
Takes a domain name and returns an IP address - like looking up a business name to find their phone number. This is the DNS lookup your browser performs every time you visit a website.
Reverse DNS (PTR records)
Takes an IP address and returns a domain name - like having a phone number and wanting to know what business it belongs to. This is what this tool performs.
Unlike forward DNS records, which are managed by whoever owns the domain, PTR records are controlled by whoever controls the IP address block - typically a hosting provider, ISP, or cloud platform. That's why you can't set your own PTR record the way you'd add an A record in your domain's DNS zone; you generally need to request it from your IP's provider.
Why Reverse DNS Matters for Email Deliverability
Reverse DNS is one of the oldest and most widely trusted signals used by receiving mail servers to judge whether an incoming message is legitimate. When a mail server connects to deliver a message, many receiving servers perform a PTR lookup on the sending IP. A missing or mismatched PTR record is one of the most common causes of email being rejected outright or routed straight to spam by major providers like Gmail and Microsoft 365.
Mail infrastructure teams often go a step further and check Forward-Confirmed reverse DNS (FCrDNS): the PTR record for the sending IP is looked up to get a hostname, and then that hostname is looked up via its A record to confirm it resolves back to the same original IP. Both directions have to agree for FCrDNS to pass. Receiving mail servers treat FCrDNS as a strong baseline authenticity check, because it confirms the IP and hostname are genuinely linked in both directions rather than one side pointing to something unrelated.
If you manage your own mail server, use this tool to confirm your sending IP's PTR record resolves to the hostname you expect before troubleshooting deliverability issues elsewhere.
Verifying Search Engine Crawlers with Reverse DNS
Reverse DNS is also the standard technique for confirming that a request claiming to be from Googlebot, Bingbot, or another search engine crawler is genuine rather than a spoofed user agent. The verification is a two-step process:
- Run a reverse DNS lookup on the crawler's IP address and note the returned hostname.
- Run a forward DNS lookup on that hostname and confirm it resolves back to the original IP.
Both checks have to pass - a genuine Googlebot IP will resolve to a hostname ending in googlebot.com or google.com, and that hostname will resolve straight back to the same IP. If either step fails, the request is not from a legitimate crawler, regardless of what its user-agent string claims.
Common Use Cases for Reverse IP / PTR Lookups
Mail Server Verification
Confirm your outbound mail server's PTR record resolves to the expected hostname before diagnosing spam-folder or bounce issues.
Bot & Crawler Authentication
Verify that traffic claiming to be a search engine crawler is actually coming from that crawler's real, published IP ranges.
Readable Server Logs
Convert raw IP addresses in access logs into readable hostnames to quickly spot which networks or providers traffic is coming from.
Network Troubleshooting
Tools like traceroute display reverse hostnames for each network hop, helping you understand which providers a route passes through.
IP Reputation & Fraud Checks
A missing, generic, or mismatched PTR record can be one signal among several when assessing whether traffic from an IP looks legitimate.
CDN & Cloud Host Identification
Reverse hostnames often reveal which hosting provider or CDN an IP belongs to, useful when investigating unfamiliar traffic sources.
Running a Reverse DNS Lookup from the Command Line
This tool gives you an instant browser-based result, but the same PTR query can be run from a terminal on any operating system:
Windows
nslookup 8.8.8.8
Automatically detects the input is an IP and performs a PTR query.
macOS / Linux
dig -x 8.8.8.8 +short
The -x flag converts the IP to in-addr.arpa notation automatically.
Quick Fallback
host 8.8.8.8
A shorter command that returns the PTR result directly.
All three commands work for IPv6 addresses too, with no special syntax required beyond the IPv6 address itself. If any of them return NXDOMAIN or no answer, no PTR record currently exists for that IP - the same result this web tool reports as "no PTR record found."
Limitations: What This Tool Does Not Do
- Not every IP address has a PTR record - many hosts intentionally leave reverse DNS unconfigured, and that is not itself an error.
- This tool checks IPv4 addresses only; IPv6 reverse lookups use the same underlying concept against the ip6.arpa zone but aren't supported in this interface.
- A successful PTR lookup only confirms the IP-to-hostname mapping - it does not by itself prove FCrDNS; you'd need to separately confirm the hostname resolves back to the same IP.
- This tool cannot enumerate every website hosted on a shared IP address - that requires a commercial co-location or hosting-history database, not a PTR query.
- PTR records require the IP owner to configure them; on dynamic or consumer IPs, results are often generic ISP-assigned hostnames rather than anything meaningful.
Frequently Asked Questions
Why does my IP show no PTR record?
Not every IP is required to have one. Reverse DNS is configured by the entity that controls the IP block - usually your hosting provider or ISP - and many consumer or non-mail-serving IPs simply don't have a PTR record set up. This is normal, though it's a problem specifically for mail servers.
How do I set up or change a PTR record?
You'll need to contact whoever controls the IP address - your hosting provider, cloud platform, or ISP - since PTR records live in a reverse DNS zone you typically don't manage directly, unlike your domain's own DNS records.
Does a missing PTR record mean my email will be rejected?
It significantly increases the risk. Many receiving mail servers treat a missing or mismatched PTR as a strong spam signal, and some reject connections outright if no PTR record is present at all.
Can I look up an IPv6 address with this tool?
This interface currently accepts IPv4 addresses only. IPv6 reverse lookups use the same PTR concept against the ip6.arpa zone and can be run with the same dig -x or nslookup commands shown above.
Is this the same as looking up who owns an IP address?
Not exactly. A PTR lookup returns the hostname configured for that IP, which often hints at the hosting provider or organization behind it, but for definitive ownership information you'd want a WHOIS lookup instead.
How long does a PTR record change take to propagate?
Reverse DNS zones can be cached for hours by resolvers, so a newly configured or updated PTR record may not show up immediately in a lookup - give it time before assuming the change failed.