DNS Tools
REVERSE DNS (PTR)

Reverse DNS Lookup

Find the PTR record of an IP address, or of every address of a host, and see whether forward DNS agrees with it.

Run Reverse DNS (PTR) lookup

No sign-up required. Public hosts and addresses only; results show what was observed, nothing is simulated.

What a reverse DNS lookup shows

Forward DNS maps a name to an address. Reverse DNS goes the other way: it asks which name a given IP address claims. The answer is a PTR record stored in a special zone, in-addr.arpa for IPv4 and ip6.arpa for IPv6, where the address is written backwards. The address 192.0.2.25, for example, is looked up as 25.2.0.192.in-addr.arpa.

This tool accepts an IP address or a host name. For a host name it first looks up the A and AAAA records, keeps only public addresses, then queries the PTR record of each one. Private and reserved addresses are never queried. For every PTR name found, it performs a second step called forward confirmation: it resolves that name and checks whether the result includes the original address.

How to read the results

Three outcomes carry meaning. A PTR name whose own A or AAAA record contains the address passes forward confirmation, often shortened to FCrDNS. A PTR name that resolves to other addresses fails confirmation. An address with no PTR record at all is reported as such, and is not by itself an error.

  • Forward-confirmed: reverse and forward DNS agree, which is what receiving mail systems usually look for.
  • PTR does not resolve back: the name exists but does not point at this address, so the pair is inconsistent.
  • No PTR: the address owner has not published one. Harmless for a web server, often a problem for a mail server.
  • Multiple PTR records: several names for one address make receiver checks inconsistent; one name matching the mail host is cleaner.
  • Generic name: names built from the address or keywords such as dynamic or customer indicate a provider pool; many mail receivers distrust mail from them.

Who controls a PTR record

The PTR zone for an address block is delegated to whoever holds the block, normally the internet service provider, hosting company or cloud vendor, not to the owner of the domain. That is why you cannot fix a PTR record in your domain's DNS panel. You request the change from the provider, or use a control-panel field some providers offer for exactly this purpose.

Reverse DNS is also not authentication. A PTR name is a claim made by the address owner, and the forward lookup only confirms that the claim and the forward zone agree. It does not prove who operates the server.

Why reverse DNS matters for email

Mail receivers frequently check the sending address: does it have a PTR, and does that name resolve back? A missing or mismatching PTR contributes to rejection or spam scoring, particularly when the name is also unrelated to the name the server announces in its greeting. It is one signal among many and does not replace SPF, DKIM or DMARC.

For websites and most other services PTR records have little practical effect, though they make logs and diagnostics more readable.

How to fix reverse DNS safely

Prerequisites: a stable sending IP, a host name you control that you want to be the public identity of the server, and an A or AAAA record for that name pointing to the IP. Risk: the PTR name becomes the identity other systems associate with the address, so changing it affects anything that matches on it. Rollback: ask the provider to restore the previous value, and keep a note of it.

  1. Create or confirm the forward record, for example mail.example.com with an A record to the sending address.
  2. Ask the address owner, or use the provider's control panel, to set the PTR of the address to that name.
  3. Keep one PTR record per address and use the same name in the mail server's greeting.
  4. Allow for caching, then run dig -x 192.0.2.25 +short and resolve the returned name; the second answer must contain the original address.
  5. Re-run this tool and confirm the result is forward-confirmed.

Limits

Answers come from the system resolver at the time of the check and may be cached, so a very recent change might not appear yet. The tool tests only the addresses it finds or is given. It does not test mail delivery, SMTP greeting names or blocklist status; use the mail diagnostics for those. A passing result means the two directions agree, not that the address has a good sending reputation.

Frequently asked questions

Why does my IP have no PTR record?

The owner of the address block has not published one. Many providers publish none by default for customer addresses; you ask them to add it.

Can I set the PTR record in my own domain's DNS?

Not unless the reverse zone is delegated to you, which is unusual. The record lives in the provider's reverse zone.

What does forward-confirmed reverse DNS mean?

The address has a PTR name, and that name resolves back to the same address. Both directions agree.

Do web servers need a PTR record?

Rarely. It matters mostly for mail-sending addresses and for readable logs.

Why do I see several PTR names?

Some addresses carry more than one for historical or shared-hosting reasons. For mail, a single name that matches the server's greeting is cleaner.

Is a PTR name proof of who owns the server?

No. It is a statement by the address owner. It can name any host, which is why the forward check exists.

Scope of this tool

  • PTR records are controlled by the address owner.

Written by DNS Tools editorial · Last updated 2026-10-09