Domain Tools
Reverse DNS Lookup
Look up the hostname associated with an IP address.
Enter an IP address to look up its associated hostname (PTR record).
Enter an IP address (or a domain, to look up its IP first).
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View all 12JustChecker tracks your server's DNS configuration continuously.
What Is Reverse DNS?
Normal DNS turns a name into an IP address; reverse DNS (a PTR record) turns an IP address back into a hostname. This tool looks up the PTR record for an IP address.
When to Use It
- When setting up a mail server - many receivers reject mail from IPs without matching reverse DNS.
- To identify which provider or host owns an IP in your logs.
How to Use It
- Enter an IPv4 or IPv6 address (or a domain to look up its IP first).
- Read the returned hostname.
Understanding the Result
Hostnames like ec2-3-110-1-2.ap-south-1.compute.amazonaws.com show the provider and region. For mail servers, the PTR hostname should resolve back to the same IP (forward-confirmed reverse DNS).
Limitations
PTR records are set by whoever owns the IP block (usually the hosting provider), not by the domain owner. Many IPs have no PTR record.
Frequently Asked Questions
It's commonly used by mail servers as a spam-fighting signal (checking that a sending server's IP resolves back to a legitimate-looking hostname), and by network administrators for diagnostics and logging.
Reverse DNS (a PTR record) must typically be configured by whoever controls the IP address block - often your hosting provider or ISP - rather than something you set directly through your own domain's DNS zone.
For a standard website, generally no direct impact - reverse DNS matters most for outbound mail server reputation, where many receiving mail servers specifically check for a matching, legitimate-looking PTR record.
Unlike forward DNS (where one hostname can have multiple IPs), an IP address conventionally has exactly one PTR record pointing to a single hostname - this is a deliberate constraint of how reverse DNS is structured.
If your hosting provider controls the IP block and hasn't configured a custom PTR record for your specific server, the reverse DNS often defaults to the provider's own generic hostname pattern for that IP range.
No - an A record maps a hostname to an IP address (forward direction); reverse DNS (a PTR record) maps an IP address back to a hostname (the opposite direction), and the two are configured completely independently.
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