Reverse DNS lookup
Find the hostname an IP address maps back to. Enter an IPv4 or IPv6 address and we look up its PTR record from a public resolver.
Related tools: DNS lookup · A record lookup · CNAME lookup · NS lookup · TXT record lookup · CAA record lookup · DNS propagation checker · All free tools
The name behind an address
Forward DNS turns a name into an address; reverse DNS turns an address back into a name, through a PTR record published under in-addr.arpa for IPv4 or ip6.arpa for IPv6. The record is controlled by whoever owns the address block, usually a hosting provider or ISP, not by the domain's owner. This tool builds the reverse name for the address you enter and asks Cloudflare's 1.1.1.1 resolver for its PTR record.
Reverse DNS is set once and rarely changes. The forward records your visitors depend on change more often, and Upcheck re-resolves them every 6 hours and alerts your team when one moves.
Three steps, no signup
- 01
Enter an IP address
IPv4 like 1.1.1.1 or IPv6 like 2606:4700:4700::1111.
- 02
We build the reverse name
Octets reversed under in-addr.arpa, or nibbles reversed under ip6.arpa, then queried over DNS-over-HTTPS.
- 03
The hostname comes back
Or a clear 'no PTR record' if the address block's owner hasn't published one.
Frequently asked questions
What is reverse DNS used for?
Mostly for mail. Receiving mail servers look up the PTR record of the connecting IP address and many reject or heavily penalise connections from addresses with no reverse DNS, or with a PTR that doesn't resolve forward to the same address. It also shows up in server logs and traceroutes, where a hostname is easier to read than a bare address.
How do I set a PTR record for my server?
Through whoever assigned the IP address. Reverse zones belong to the address block, so your hosting or cloud provider controls them; most expose a 'reverse DNS' or 'PTR' setting on the server or IP. You can't set it in the zone for your domain. After setting it, make the hostname's forward A or AAAA record point back at the same address, which is what forward-confirmed reverse DNS means.
Why does the lookup return no PTR record?
Because none is published for that address, which is common for consumer connections, cloud instances with no reverse DNS configured, and address space that isn't in use. For a web server it is harmless. For a mail server it is a deliverability problem: set one with your provider.
Can one IP address have several PTR records?
Technically yes, and the tool shows all of them, but it is a bad idea for mail: receivers pick one arbitrarily and check that it resolves forward to the address. Publish a single PTR that matches the hostname your mail server introduces itself with.
Is this reverse DNS lookup free?
Yes. No account, no limit on lookups by hand; scripted use is rate limited. Upcheck's paid monitoring watches the forward records for every website you add, every 6 hours, and alerts your team when one changes.
One lookup finds the name. Monitoring watches the records that matter.
Add your websites to Upcheck and get alerted by email, Slack, Discord, Teams, or webhook when their DNS changes.