SOA Lookup
Read the Start of Authority record (serial, refresh…).
Enter a value above to run SOA Lookup
e.g. example.com
Quick answer
An SOA lookup reads a domain's Start of Authority record, which holds core zone settings like the primary name server, the admin contact, the serial number, and the refresh and TTL timers. The serial number changes each time the zone is edited, so it shows whether secondary servers are up to date.
The SOA (Start of Authority) record sits at the top of every DNS zone and defines who is responsible for it and how the zone is versioned and cached. This tool queries the SOA record for a domain and shows the primary nameserver, the responsible party's email, the serial number, and the four timers that control how secondary nameservers refresh and how long negative answers are cached. If you run your own DNS, delegate to a provider, or troubleshoot slow propagation, reading the SOA is the first step to understanding how a zone behaves.
How to read the results
The MNAME is the primary (master) nameserver for the zone. RNAME is the administrator's email, written with the first dot standing in for the @ sign (admin.example.com means [email protected]). The serial number is the zone's version; secondaries only pull updates when it increases. Refresh, Retry, and Expire (in seconds) govern how secondaries sync with the primary, and the final value, Minimum TTL, sets how long NXDOMAIN (negative) responses are cached by resolvers.
Why it matters
The serial number is your fastest way to confirm a zone change actually took effect: if you edited records but the serial did not bump, secondaries never pulled the update. The Expire timer decides how long secondaries keep serving a zone if the primary goes dark, and the Minimum TTL controls how long a mistaken NXDOMAIN lingers in caches. Registrars and some validators also flag SOA problems, so a clean, well-formed SOA is part of a healthy delegation.
Common problems & fixes
If a change is not propagating, check that the serial number increased; many hidden-primary setups won't notify secondaries otherwise. Different nameservers returning different serials means the zone is out of sync, so wait for a refresh cycle or trigger a transfer. A very high Minimum TTL keeps negative caching around too long during migrations. Use the common YYYYMMDDnn serial format so each edit is obviously newer than the last.
Frequently asked questions
- What does the serial number tell me?
- It is the version stamp of the zone. Every time you edit records, the serial should increase. Secondary nameservers compare their stored serial against the primary's; they only request a zone transfer when the primary's number is higher. If your serial never changed after an edit, your update likely never reached the secondaries.
- Why is the admin email written with dots?
- DNS uses the @ character as a field separator, so it cannot appear inside an SOA RNAME. The first dot in the RNAME represents the @ instead. So hostmaster.example.com maps to [email protected]. If the local part itself contains a dot, it is escaped in the record, though that is rare in practice.
- What is the Minimum TTL used for?
- Despite the name, in modern DNS the SOA's final field sets the negative caching TTL: how long resolvers remember that a name does not exist (NXDOMAIN). A high value means a newly created record may stay invisible for a while after resolvers cached its absence. Lower it before adding records during a migration to speed up visibility.