↑↓ to move · Enter to open · Esc to close

SOA Record Lookup

An SOA record lookup explains the zone serial, the primary server, the responsible mailbox, and the refresh, retry, expire, and minimum timers.

This check runs on our server. The address you enter is used only for this check and is not stored.
Updated

This check runs on our server. The address you enter is used only for this check and is not stored.

How to use the SOA Record Lookup

  1. Enter the zone name, usually the registered domain.
  2. Pick a resolver. The authoritative choice reads the SOA from the zone's own servers.
  3. Tick the robot check and press Look up.
  4. Each field has a one-line note on what the number is for.

How it works

This check runs on our server. The name is not stored.

Every zone has one SOA. The serial is a counter that secondary servers compare. When the serial matches YYYYMMDDnn, the tool also prints it as a date and a sequence, for example 2024010101 as 2024-01-01, sequence 1. A serial that is just a number stays a number. The mailbox is shown with @. In a zone file the same address is written with a dot in place of @, so hostmaster.example.com is [email protected].

Refresh, retry, and expire are seconds. They tell a secondary server how to keep its copy. The minimum field is the time resolvers may cache a "name not found" answer.

Examples

  • Serial 2024010101 is shown as the date 2024-01-01, sequence 1.
  • Serial 42 stays "42". It does not match the date form, so no date is invented.
  • Refresh 7200 is two hours: a secondary asks for a new serial on that interval.

Limitations

  • A date reading is only a convention. The serial is still a counter, and some operators use a plain integer.
  • The page does not compare your serial with a secondary's copy. The propagation checker is the tool for "who has the new value."
  • One SOA is returned. Extra SOA records in an answer are unusual and would each get a field list.

Frequently asked questions

What is the SOA serial for?

Secondaries store the last serial they copied. When the primary's serial is higher, they transfer the zone again.

How do I read the mailbox?

The tool shows the mailbox with @. In a zone file, the first dot stands for @, so admin.example.com is [email protected].

What happens when expire is reached?

A secondary that has not been able to refresh stops serving the zone, so it does not keep handing out a copy that may be abandoned.

Often used together with the SOA Record Lookup.

  • NS Lookup

    Name servers from the NS records, with TTL.

  • DNS Lookup

    One table of A, AAAA, MX, NS, TXT, SOA, and CAA records for a domain.

  • DNS Propagation Checker

    One DNS question sent to about 20 public resolvers, with a match against the value you expect.