Our free reverse DNS lookup tool lets you instantly convert IP addresses to hostnames by checking PTR (pointer) records. Whether you need to verify a single IP address or perform bulk reverse DNS lookups on an entire range, this tool supports multiple input formats including CIDR notation, IP ranges, and batch processing up to 256 addresses. Reverse DNS is essential for email server validation, network troubleshooting, security investigations, and infrastructure mapping. Use this PTR record checker to identify mail servers, verify legitimate hosts, detect suspicious activity, or document your network. Supports both IPv4 and IPv6.
Unique feature:
Unlike most free reverse DNS tools, this page supports batch processing up to 256 IPs at once using CIDR notation or IP ranges.
Reverse DNS Search
Batch Processing
Resolve multiple IPs with CIDR range support
Network Mapping
Identify host patterns and infrastructure setup
Security Validation
Verify legitimate servers and detect suspicious hosts
How to use reverse DNS lookup
This tool accepts multiple input formats:
- Single IP: Enter any IPv4 (e.g., 8.8.8.8) or IPv6 address.
- IP Range: Use short format (192.168.1.1-30) or full format (192.168.1.1-192.168.1.30).
- CIDR notation: Enter subnet notation (e.g., 192.168.1.0/24) for bulk lookups.
- Click Search and review PTR results.
Input format comparison
| Format | Example | IPs checked | Best for |
|---|---|---|---|
| Single IP | 8.8.8.8 | 1 | Quick hostname verification |
| Short range | 192.168.1.1-30 | 30 | Checking a specific server range |
| Full range | 192.168.1.1-192.168.1.30 | 30 | Explicit IP boundaries |
| CIDR /32 | 192.168.1.1/32 | 1 | Single IP in CIDR format |
| CIDR /28 | 192.168.1.0/28 | 16 | Small subnet checks |
| CIDR /24 | 192.168.1.0/24 | 256 | Full Class C network |
Understanding PTR records
PTR (Pointer) records are the DNS record type used for reverse DNS lookups. While A/AAAA records map domains to IP addresses (forward DNS), PTR records do the opposite—they map IP addresses back to domain names. Typically, PTR records are managed by whoever controls the IP address (your ISP or hosting provider). For email deliverability, PTR and A/AAAA records should align (forward-confirmed reverse DNS).
If you need to generate reverse DNS zone entries, try our PTR Record Generator.
Reverse DNS best practices
- Email servers: Ensure your PTR record matches your mail hostname and that hostname has a matching A/AAAA record (FCrDNS).
- Security: Investigate IPs without hostnames in logs and cross-check ownership with IP WHOIS Lookup.
- DNS hygiene: Use smaller ranges (20–50 IPs) for faster, focused investigations.
- Mail troubleshooting: Validate your full email setup with Email Validator.
Common Questions About Reverse DNS Lookup
What is Reverse DNS Lookup?
Reverse DNS lookup converts IP addresses into their corresponding hostnames by checking PTR records. Instead of looking up a domain name to find an IP address (forward DNS), reverse DNS does the opposite—it looks up an IP address to find its associated hostname.
Why would I need to use Reverse DNS?
Reverse DNS is useful for verifying email server configurations, investigating suspicious network activity, validating infrastructure, and troubleshooting connectivity issues. It’s especially important for mail servers because missing or mismatched PTR records can hurt deliverability.
What’s the difference between DNS and Reverse DNS?
Forward DNS converts domain names to IP addresses (A/AAAA records). Reverse DNS converts IP addresses back to hostnames using PTR records. Both are part of the same DNS system but answer different questions.
What formats can I use for IP ranges?
You can enter a single IP, a short range (192.168.1.1-30), a full range (192.168.1.1-192.168.1.30), or CIDR notation (192.168.1.0/24). For performance, requests are limited to 256 IPs (a /24) or less.
Why do some IPs have no hostname?
Not every IP address has a PTR record configured. This can happen if the owner hasn’t set reverse DNS, the address is private, or it’s intentionally left without a hostname. If you control the IP range, you can create PTR records.
How do I fix missing PTR records?
PTR records are controlled by whoever owns the IP range (usually your ISP or hosting provider). Contact them with the IP and desired hostname. If you manage your own IP block, configure reverse zones yourself or generate zone entries with a PTR record generator.
Can I perform reverse DNS on IPv6 addresses?
Yes. Reverse DNS works for both IPv4 and IPv6. IPv4 uses the in-addr.arpa zone, while IPv6 uses ip6.arpa. The lookup concept is the same: PTR records map an IP back to a hostname.
Related tools
- DNS Records Lookup — check forward DNS records
- DNS Propagation Checker — verify DNS changes globally
- PTR Record Generator — generate reverse DNS zone entries