GATE 09 · DNS LOOKUP
Look up DNS records
Quick answer: A DNS lookup shows the records stored for a domain name, such as the addresses hosting the site, the servers that accept its email and its text records. Choose a domain and a record type, or run a reverse lookup on an IP address. The tool asks public DNS resolvers on your behalf.
Enter a domain and a record type, or choose reverse (PTR) to find the name registered for an IP address.
Queries are answered by the public resolvers 1.1.1.1 and 8.8.8.8, so you see what they return right now. Only public domain names are looked up: internal names such as .local, .internal and .lan are rejected. The tool allows 20 lookups a minute per visitor.
What a DNS lookup shows
DNS is the system that turns a name such as example.com into the details computers need: which addresses host the website, which servers accept its email, and which text records prove who controls it. A DNS lookup asks the system for one type of record about one name and shows the answer.
Choose a domain and a record type and the tool asks public DNS resolvers on your behalf. It can also run a reverse lookup, which goes the other way: given an IP address, it asks which name the address's owner has registered for it.
Record types
- A and AAAA: the IPv4 and IPv6 addresses of a name. TTLs are shown for these.
- MX: the mail servers for a domain, with a priority number. Lower numbers are tried first.
- TXT: free-form text, used for email policies such as SPF and for proving ownership to other services.
- NS: the name servers responsible for the domain.
- CNAME: an alias that points one name at another.
- SOA: the start-of-authority record, with the primary name server, a contact and timing values.
- CAA: which certificate authorities may issue certificates for the domain.
How the lookups are made
Queries go from our server to the public resolvers 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google), with short timeouts. The result is what those resolvers return right now, which can differ from what your own resolver returns if records were changed recently, because answers are cached for as long as each record's TTL allows.
To keep the tool safe, names are checked strictly. Internal or local-looking names such as ones ending in .local, .internal or .lan, single-word names and IP addresses typed as names are rejected, and the tool allows 20 lookups a minute for each visitor.
When to use it
- After changing a website's hosting, to see whether the new addresses are visible yet.
- When email to a domain bounces, to check that its MX records point where you expect.
- When setting up SPF, DKIM or domain verification, to confirm that a TXT record was saved correctly.
- When a certificate request is refused, to read the domain's CAA record.
- To find out who runs a domain's DNS, by reading its NS and SOA records.
Reverse DNS
Reverse DNS maps an IP address to a name through a PTR record. Mail servers use it to judge senders, and network operators use it for logs. Many addresses have no PTR record, and the name can say little about who is really using the address.
Frequently asked questions
What does TTL mean?
TTL, or time to live, is the number of seconds a resolver may keep an answer before asking again. A short TTL means changes spread quickly. A long one means old answers can linger. We show it for A and AAAA records.
Why do I see different results from my own computer?
Different resolvers can hold older or newer copies of a record until its TTL runs out. Your own router or provider may also filter or rewrite some answers. This tool shows what Cloudflare and Google return.
Why does a lookup say there are no records?
The name exists but has no record of that type, or the name does not exist at all. For example, many domains have no CNAME or no AAAA record.
Why was my name rejected?
Only valid public domain names are looked up. Names without a dot, internal-looking names such as printer.local, and names with invalid characters are rejected.
What is a PTR record?
A PTR record is the reverse of an address record. It stores the name that an IP address's owner has chosen for that address, and is used for reverse DNS.
Is my search stored?
No results are saved. The name you type is part of the request, so it appears in our normal web server log for about two weeks, as described on the privacy page.