Give it a hostname and it returns the addresses that name resolves to. Give it an address and it looks for a name pointing back. The two directions are configured separately in DNS, so they often disagree, and the disagreement is usually the interesting part.

How to use

Enter one hostname or one IP address. For the address your own connection is using, the public IP page answers that instead.

Forward and reverse are two separate records

A name pointing at an address and that address pointing back at a name are configured independently, often by different people. The forward record belongs to whoever runs the domain. The reverse record belongs to whoever owns the address block, which is usually the hosting provider. Mail systems care about the pair matching, and that is where most people first meet the distinction.

One name, many addresses

Getting several addresses back is normal for anything behind a CDN or a load balancer, and the set you receive can differ from the set someone in another country receives. That is deliberate: the resolver is being pointed at whatever is nearest. It also means an allowlist built from today's addresses will break quietly when the provider changes them.

Where the answer comes from

The lookup runs on our server against public DNS, so your hosts file, your VPN's private resolver, and your company's internal zones are all invisible to it. That is a limitation and also the point. When a colleague can reach a host and you cannot, comparing what a neutral resolver sees is how you find out which side is holding the unusual answer.

FAQ

Can it tell me where a server is located?

Not reliably. This reports naming, not geography, and the commercial databases that guess location are a separate class of tool with their own error rates.

Why does the reverse lookup come back empty?

Because reverse records are optional and many address blocks have none. An empty result is normal rather than a failure.

Will it resolve an internal hostname?

No. Our server queries public DNS, and a name that only exists on your network does not exist there.

It returned several addresses for one name. Which is the real one?

All of them. Large sites publish many addresses on purpose so that load spreads and one failure is not fatal.

Related tools

Network and domain tools
DNS Lookup
Public A, AAAA, CNAME, MX, TXT and NS records.
What Is My IP
The public IP our server sees for your connection.
Open Port Checker
Try one TCP connection to a host and port.
HTTP Header Checker
Read the response headers a URL returns.
SSL Certificate Checker
Read the certificate a host presents over TLS.