What is an SOA Record in DNS?

SOA stands for Start of Authority. Every DNS zone must have exactly one SOA record at the beginning of the zone file. It provides essential information about the zone's management, the primary nameserver, and how secondary servers should cache the domain's information.

Verify your Zone Authority

Check your DNS serial number and timers to troubleshoot zone transfer and propagation issues.

Check SOA Records Online

The Anatomy of an SOA Record

An SOA record consists of several distinct fields that dictate how your DNS zone is managed:

  • Primary MNAME: The hostname of the primary nameserver for the zone.
  • Responsible RNAME: The email address of the person responsible for the zone. Note that in DNS, the @ is replaced by a dot (e.g., admin.example.com instead of admin@example.com).
  • Serial Number: A version number for the zone. When the serial increases, secondary servers know they need to refresh their data.
  • Refresh: How often (in seconds) secondary servers query the primary for updates.
  • Retry: How long they wait before retrying a failed refresh.
  • Expire: The maximum time secondary servers will keep serving data if the primary server is unreachable.
  • Minimum TTL: The time for which negative responses (like "record not found") are cached.

SOA Record FAQ

The serial number is the only way secondary DNS servers know that the zone has changed. If you update an A record but forget to increase the serial number in the SOA record, your changes will never propagate to the secondary servers.

A common value is 1 to 4 weeks (e.g., 2419200 seconds). If your primary server goes down, this timer starts. If it isn't fixed before the timer runs out, your secondary servers will stop answering queries, making your domain go completely offline.