Reverse DNS Lookup
Reverse DNS turns an IP address into a hostname using a PTR record. This page builds the in-addr.arpa or ip6.arpa name for the address, asks Google Public DNS for its PTR record, then checks that the hostname resolves back to the same IP, which receiving mail servers look for.
| Lookup | Question | Record |
|---|---|---|
| Forward | What is the IP of mail.example.com? | A or AAAA |
| Reverse | What hostname belongs to 192.0.2.25? | PTR |
| Forward-confirmed | Do the two answers point at each other? | PTR, then A or AAAA |
Updated
Enter an IPv4 or IPv6 address. The lookup runs over DNS-over-HTTPS from your browser to Google Public DNS, so you see the answer the public internet sees.
Reading the result
A hostname with a green confirmed mark means the PTR and the forward record agree, which is what mail checks want. A hostname that does not confirm usually means the A record was never added or points elsewhere.
No answer at all is reported as either no PTR record or a missing reverse zone. Either way, the fix is with the IP's owner, not with your domain registrar.
How it works
- Type an IP address such as 8.8.8.8.
- The page reverses it into a lookup name, for example 8.8.8.8.in-addr.arpa, or a nibble-by-nibble ip6.arpa name for IPv6.
- It asks for the PTR record and lists every hostname returned.
- For each hostname it asks for the A or AAAA record and marks whether it points back to the address you entered.
Tips
- PTR records are set by whoever controls the IP block, usually your host or internet provider, not in your domain's DNS. Ask them, or use the reverse DNS setting in your server panel.
- For a server that sends email, make the PTR hostname one you control (for example mail.example.com) and give that hostname an A record with the same IP.
- Generic hostnames full of numbers look like home connections to spam filters. A named hostname on your own domain looks like a real mail server.
- One PTR per address is the norm. Several can confuse checks that only read the first answer.
Frequently asked questions
Why does reverse DNS matter for email?
Gmail's sender guidelines require sending servers to have valid forward and reverse DNS, and many other providers check it too. Mail from an address with no PTR, or a PTR that does not resolve back, is more likely to be rejected or filed as spam.
Who can set a PTR record?
Whoever the reverse zone for the IP block is delegated to, which is the organisation holding the block. On cloud and VPS hosts there is usually a reverse DNS field in the control panel; with an internet provider you ask support.
Does my website need reverse DNS?
No. Browsers never check it. It matters for mail servers and for some logging and security tools. Shared and CDN-hosted sites usually show the provider's hostname, and that is fine.
What does 'no PTR record' mean?
The reverse zone exists or the name does not, but nobody has published a hostname for that address. It is common for home and mobile connections and for unused cloud addresses.
Related: SPF, DKIM, DMARC and MX checker, IP WHOIS lookup, Google Workspace MX records, Set up DKIM at GoDaddy, DNS record types.
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