Reverse DNS Lookup - Find Hostname from IP Address
No logs stored • Server-side processing
Convert any IP address to its hostname with automatic forward verification. Supports IPv4 and IPv6 with FCrDNS validation to confirm proper DNS configuration.
Free Online PTR Record Checker
Find Hostname from IP
Enter an IP address to lookup its PTR record
What is Reverse DNS and How Does PTR Lookup Work?
Reverse DNS (rDNS) is the process of converting an IP address back to its associated hostname. While regular DNS resolves domain names to IP addresses (google.com → 142.250.x.x), reverse DNS does the opposite: IP → hostname. This lookup queries PTR (Pointer) records stored in special reverse DNS zones: in-addr.arpa for IPv4 and ip6.arpa for IPv6.
What You'll Discover
Can Find
- PTR hostname for any public IP address
- Forward verification status (FCrDNS pass/fail)
- Reverse DNS zone (in-addr.arpa or ip6.arpa)
- TTL (Time To Live) for PTR record
- Multiple PTR records when present
Cannot Find
- All domains hosted on an IP (use Reverse IP Lookup)
- Blocklist/blacklist status
- Port scan or service detection
- Historical PTR records
How to Check PTR Records for Any IP
Find the hostname associated with any IP address in seconds with automatic forward verification.
Enter IP Address
Type any IPv4 address (e.g., <code>8.8.8.8</code>) or IPv6 address (e.g., <code>2001:4860:4860::8888</code>) into the input field. Private IPs work too, though they typically don't have PTR records.
Click Lookup
Press the 'Lookup' button to query the PTR record from the reverse DNS zone. Our tool automatically determines the correct reverse zone based on the IP version.
View PTR Hostname
See the hostname returned from the PTR record lookup. If no PTR exists, you'll see a clear 'No PTR Record' status with an explanation.
Check Forward Verification
Review the FCrDNS (Forward-Confirmed reverse DNS) status. A 'Verified' badge means the hostname resolves back to the original IP—essential for email deliverability.
Understanding Your Reverse DNS Results
Each result shows the PTR hostname along with verification status and technical details.
PTR Hostname
The hostname returned from the PTR record lookup. This is the name associated with the IP address in the reverse DNS zone. For well-configured servers, this typically matches the server's primary hostname.
dns.google
Forward Verified
Indicates whether the PTR hostname resolves back to the original IP address (FCrDNS). A 'Verified' status means the DNS is properly configured bidirectionally—critical for email servers.
✅ Verified
Reverse Zone
The DNS zone queried for the PTR lookup. IPv4 uses in-addr.arpa with octets reversed (8.8.8.8 → 8.8.8.8.in-addr.arpa). IPv6 uses ip6.arpa with each hex nibble reversed.
8.8.8.8.in-addr.arpa
IP Version
Whether the IP is IPv4 (32-bit, dotted decimal) or IPv6 (128-bit, hexadecimal colon notation). The lookup process differs slightly between versions.
IPv4
TTL
Time To Live—how long DNS resolvers should cache this PTR record. Displayed in human-readable format (e.g., 1h, 24h). Shorter TTLs allow faster updates.
24h
Status
Overall PTR configuration status. 'PTR Configured' means a hostname was found; 'No PTR Record' means no reverse DNS is set up for this IP.
PTR Configured
Why Choose Our Reverse DNS Lookup Tool
Comprehensive PTR record checking with automatic verification and clean results.
Automatic Forward Verification
FCrDNS check automatically verifies that the PTR hostname resolves back to the original IP. Essential for email deliverability diagnostics.
Visual Verification Diagram
Step-by-step visualization showing IP → PTR → Hostname → A/AAAA → IP with match/mismatch status for easy understanding.
IPv4 & IPv6 Support
Full support for both IP versions with proper zone handling. IPv4 uses in-addr.arpa, IPv6 uses ip6.arpa with nibble reversal.
Private IP Detection
Automatically detects RFC 1918 private addresses (10.x.x.x, 172.16-31.x.x, 192.168.x.x) and provides helpful messaging.
Multiple PTR Support
Displays all PTR records when an IP has multiple hostnames configured. Each record can be copied individually.
Export & Share
Export results in JSON, CSV, or plain text format. Share via URL parameters for easy collaboration.
When You Need Reverse DNS Lookup
Essential scenarios where checking PTR records matters for your infrastructure.
Email Deliverability
Verify your mail server has a valid PTR record. Many spam filters reject emails from IPs without proper reverse DNS. FCrDNS (matching PTR and A records) is essential for inbox delivery.
Security Auditing
Check that server IPs have proper reverse DNS configuration as part of security assessments. Anomalous or missing PTR records can indicate misconfiguration or suspicious infrastructure.
Network Troubleshooting
Diagnose DNS issues by verifying PTR records are correctly configured. Identify hostname-IP mismatches that could cause authentication or connectivity problems.
Server Configuration
Confirm PTR records match your server hostnames after initial setup or IP changes. Proper reverse DNS is a best practice for any internet-facing server.
How Reverse DNS and PTR Records Work
Reverse DNS uses a special zone hierarchy to map IP addresses back to hostnames using PTR records.
How Reverse DNS Zones Work
Reverse DNS uses specially structured zones to enable IP-to-hostname lookups. For IPv4, the IP octets are reversed and appended to 'in-addr.arpa'. For example, 8.8.8.8 becomes a query for 8.8.8.8.in-addr.arpa. For IPv6, each hexadecimal nibble (4 bits) is reversed and appended to 'ip6.arpa'. These reverse zones are typically delegated by Regional Internet Registries (RIRs) to ISPs and hosting providers, who then manage PTR records for their IP ranges.
Forward-Confirmed Reverse DNS (FCrDNS)
FCrDNS is a two-step verification process: First, perform a PTR lookup to get the hostname for an IP. Second, perform an A or AAAA lookup on that hostname. If the resolved IP matches the original, it's 'forward confirmed'. This bidirectional match indicates proper DNS configuration and is particularly important for email servers. Many spam filters specifically check for FCrDNS as an anti-spam measure. Our tool performs this verification automatically.
Command Line Alternatives
You can perform reverse DNS lookups from command line using several tools: <code>nslookup 8.8.8.8</code> (Windows/Linux/Mac), <code>dig -x 8.8.8.8</code> (Linux/Mac, most detailed output), or <code>host 8.8.8.8</code> (Linux/Mac, simple output). These commands query the in-addr.arpa zone directly. Our online tool adds automatic FCrDNS verification, private IP detection, and export options that command-line tools don't provide.
Why PTR Records Matter for Email
Email servers rely heavily on reverse DNS for sender verification. RFC 5321 recommends that mail servers have PTR records matching their sending hostname. Without valid reverse DNS, your emails may be rejected or flagged as spam by major providers like Gmail, Microsoft 365, and Yahoo. Common issues include: missing PTR records (ask your ISP/host to add one), PTR hostname that doesn't resolve (broken DNS), or PTR that resolves to a different IP (configuration mismatch). Our tool helps diagnose all these scenarios.
Reverse DNS Lookup Specifications
- Record Type
- PTR (Pointer)
- IPv4 Zone
- in-addr.arpa
- IPv6 Zone
- ip6.arpa
- Forward Verification
- Automatic (FCrDNS)
- Timeout
- 20 seconds overall
- Cache Duration
- 1 hour
- Private IP Detection
- Yes (RFC 1918, RFC 4193)
- Multiple PTR Support
- Yes
- Export Formats
- JSON, CSV, Plain Text
- API Access
- Free, no key required
Frequently Asked Questions
What is reverse DNS lookup?
Reverse DNS lookup (rDNS) converts an IP address back to its associated hostname by querying PTR (Pointer) records. It uses special reverse zones: in-addr.arpa for IPv4 and ip6.arpa for IPv6. This is the opposite of regular DNS which converts hostnames to IP addresses.
What is a PTR record?
A PTR (Pointer) record is a DNS record type that maps an IP address to a hostname. PTR records are stored in reverse DNS zones and are typically configured by ISPs or hosting providers. They're essential for email deliverability, as many mail servers check PTR records to verify sender legitimacy.
Why is reverse DNS important for email?
Email servers use reverse DNS to verify that sending mail servers are legitimate. Many spam filters reject or flag emails from IPs without valid PTR records. A matching PTR record (where the hostname resolves back to the same IP, called FCrDNS) indicates a properly configured mail server and improves email deliverability.
What is forward verification (FCrDNS)?
Forward-Confirmed reverse DNS (FCrDNS) verifies that the hostname returned by PTR lookup resolves back to the original IP address. Our tool automatically performs this check: if 8.8.8.8 → dns.google (PTR) and dns.google → 8.8.8.8 (A record), it's verified. This bidirectional match confirms proper DNS configuration.
Why might an IP have no PTR record?
Some IPs don't have PTR records because: the ISP or hosting provider hasn't configured them, it's a dynamically assigned residential IP, it's part of a CDN or load balancer, or it's intentionally left unconfigured. Residential IPs often lack PTR records, while business and server IPs typically have them.
What is the in-addr.arpa domain?
The in-addr.arpa domain is a special DNS zone used for IPv4 reverse DNS lookups. The IP address octets are reversed and appended: 8.8.8.8 becomes 8.8.8.8.in-addr.arpa. IPv6 uses ip6.arpa with each hexadecimal digit (nibble) reversed. Our tool displays the reverse zone used for your lookup.
Can I lookup private IPs like 192.168.x.x?
Yes, you can enter private IPs, but they typically don't have PTR records in public DNS. Our tool detects private IPs (RFC 1918 addresses: 10.x.x.x, 172.16-31.x.x, 192.168.x.x) and shows an informative message explaining that PTR records are typically not configured for private addresses.
How do I check PTR from command line?
You can use: 'nslookup 8.8.8.8' (Windows/Linux/Mac), 'dig -x 8.8.8.8' (Linux/Mac, most detailed), or 'host 8.8.8.8' (Linux/Mac, simple). Our online tool adds automatic forward verification, visual diagrams, and export options that command-line tools don't provide.
What if forward verification fails?
If forward verification fails, it means the PTR hostname doesn't resolve back to the original IP. This can cause email delivery issues as many spam filters reject mail from IPs with mismatched PTR/A records. Contact your hosting provider to ensure both records are properly configured and match.
How do I set up reverse DNS for my IP?
Reverse DNS is configured by whoever controls the IP address, typically your ISP or hosting provider. Contact them to request a PTR record be added for your IP pointing to your desired hostname. Ensure your hostname's A record also points back to your IP for FCrDNS to pass.
Check PTR Records for Any IP Now
Verify reverse DNS configuration, check FCrDNS status, and troubleshoot email deliverability issues. Enter any IPv4 or IPv6 address to get started.
Lookup PTR Record