How to read a DNS lookup
Quick answer: a DNS lookup shows the public records a resolver can see for a domain at the time of the query. Start with A and AAAA for a website, MX for mail, NS for delegated name servers, TXT for verification or email policy, CNAME for aliases, and SOA for zone authority. TTL indicates how long a resolver may cache a record.
What each DNS record means
| Record | What it represents | When to check it |
|---|---|---|
| A | An IPv4 address for a hostname | A website or service does not resolve over IPv4 |
| AAAA | An IPv6 address for a hostname | IPv6 visitors reach a different or broken destination |
| MX | The mail exchangers that receive email for a domain | Incoming email is delayed or rejected |
| NS | The authoritative name servers delegated for a domain | DNS was moved to another provider |
| TXT | Text used for verification and policies such as SPF | A service cannot verify the domain or email authentication fails |
| CNAME | An alias from one hostname to another canonical name | A subdomain should follow another hostname |
| SOA | Zone authority and administrative timing data | You need to identify the zone source or compare serial data |
How to check a domain step by step
- Enter a hostname such as
example.comorwww.example.com. Do not enter a full page URL. - Select only the record types relevant to the problem. A smaller query is easier to interpret.
- Run the lookup and compare each returned value with the destination supplied by your hosting, email, or verification provider.
- Read the TTL beside the record. A recent change may not be visible everywhere until older cached answers expire.
- If the result is unexpected, compare the apex domain and the specific hostname. They can legitimately use different records.
What TTL tells you
TTL means time to live. RFC 1035 defines it as the interval a resource record may be cached before the source should be consulted again. TTL is expressed in seconds. It controls cache lifetime; it is not a countdown proving that every resolver will update at the same moment.
Lowering a TTL before a planned migration can reduce how long new answers remain cached, but only after resolvers have received the lower value. A resolver that already cached an older, higher TTL may continue using that answer until its existing cache expires.
Why two DNS tools can show different answers
DNS answers can vary because tools may query different recursive resolvers, those resolvers may hold caches created at different times, and some networks apply their own DNS behavior. Geographic routing and provider configuration can also return different valid answers. This checker sends queries through a public DNS-over-HTTPS service; RFC 8484 defines DNS queries and responses carried over HTTPS.
Common troubleshooting patterns
- Website not loading: compare A, AAAA, and any CNAME for the exact hostname visitors use.
- Email not arriving: inspect MX first, then check the TXT records required for SPF or provider verification.
- Change not visible: verify that the authoritative NS records are correct, then allow for cached answers and TTL.
- Only one hostname fails: check the failing hostname directly. The apex domain and
wwware separate DNS names. - No result returned: absence can be valid for the selected record type. Confirm the spelling and test another relevant type before concluding that the entire domain is down.
Limits of this DNS checker
This tool observes public DNS data; it does not edit records, test private split-horizon DNS, guarantee a global propagation state, or prove that an application behind an IP address is healthy. It also does not replace an authoritative provider audit. For the standardized registry of DNS record types, see the IANA DNS Parameters.
Frequently asked questions
Why do DNS lookup results differ between tools?
Different tools can query different recursive resolvers with different cached data. During a change, TTLs and query time can therefore produce different answers. Compare more than one resolver when diagnosing propagation.
What does TTL mean in DNS?
TTL is the number of seconds a resolver may cache a DNS record before consulting the source again. A lower TTL can shorten cache lifetimes, but it cannot force every resolver to refresh immediately.
Which records should I check if a website works but email does not?
Check MX first, then TXT for SPF or verification and any CNAME records required by the mail provider. A and AAAA can be correct while mail routing or authentication records are wrong.
Is this a global DNS propagation test?
No. It reports answers from one public DNS-over-HTTPS resolver at the time of the query. It is a useful observation, not proof of what every resolver worldwide currently holds.