Free tool
DNS checker
Enter a domain or subdomain to see its DNS records and compare what four public resolvers return, with warnings for the mistakes that break sites and email.
Questions
A question to the domain name system, the internet's address book. It returns the records that say where a name points, where its email goes and which servers are in charge of it.
A and AAAA records point a name at a server address. CNAME makes one name an alias of another. MX says where email is delivered. NS lists the name servers in charge of the domain. TXT holds text such as email security rules and site verification codes.
When you change a record, resolvers around the world keep the old answer until its time to live (TTL) runs out. Most changes show up within minutes to a few hours, and occasionally take a day or two. Comparing resolvers here shows whether the change has reached them yet.
Either a recent change has not reached every resolver, or the domain uses a CDN or load balancer that answers differently by location. For name server, mail and text records the answers should always match.
No. DNS has no public list of subdomains. This tool checks the exact name you type, so check each subdomain you care about on its own.
The name you look up is logged so we can see which tools are used, as our privacy policy describes. Nothing else about you is collected, and the lookup reads only public DNS.
Guides
More free tools
Email Deliverability Check
Whether your domain's SPF, DKIM and DMARC records are set up so your mail lands in the inbox, not spam.
Run the checkWebsite Security Grade
An A+ to F grade for the security headers that protect your visitors, with what each gap means.
Run the checkWhois Lookup
Registrar, domain age, expiry, status codes, name servers, DNS records and where a domain is hosted.
Run the checkNot sure your DNS is set up right?
Send us the domain. We check the records, where DNS is held and whether email is set up safely, before there is any quote.
No pitch deck, no obligation. Bring your URL and we will look at it together.