The SOA (Start of Authority) record defines core metadata for a DNS zone, including the primary name server and the zone serial. It also includes refresh and retry timers for secondary servers.
The SOA serial indicates the version of a zone. If secondary name servers are out of sync, the serial often reveals the mismatch. Use the SOA lookup tool to compare values and confirm that authoritative servers agree.
Start with the SOA lookup and verify the name servers in the NS guide. For propagation issues, compare resolvers using the DNS propagation check.
SOA works with NS records and can affect DNSSEC validation. If you use DNSSEC, review the DNSSEC lookup tool.