SOA Record Lookup
Look up the Start of Authority (SOA) record for any domain — includes primary nameserver, serial and TTL values.
About SOA Records
The SOA (Start of Authority) record is a mandatory DNS record that exists at the root of every DNS zone. It contains administrative metadata about the zone and controls how secondary DNS servers synchronise with the primary. There is exactly one SOA record per zone.
SOA record fields explained
- Primary NS (MNAME) — The primary authoritative nameserver for the zone.
- Admin Email (RNAME) — The email address of the zone administrator, encoded with the first
.representing@(e.g.hostmaster.example.com=hostmaster@example.com). - Serial — A version number that increments whenever the zone is updated. Secondary servers compare this value to decide whether to refresh. Commonly formatted as
YYYYMMDDNN(date + sequence). - Refresh — How often (seconds) secondary servers should check the primary for updates.
- Retry — How long a secondary should wait before retrying a failed refresh.
- Expire — How long a secondary may keep serving cached zone data if it cannot reach the primary.
- Minimum TTL — The minimum TTL applied to negative responses (NXDOMAIN cache time, per RFC 2308).
When SOA records matter
The serial number is critical during DNS migrations. If you move zones between providers without incrementing the serial, secondary servers may refuse to update. Always increment the serial after any zone change. The refresh, retry, and expire values are less important for modern cloud DNS providers that use API-driven replication rather than traditional zone transfers.