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The short answer: a DNS zone is a plain-text list of records, one per line, in a standard format (the “zone file” from RFC 1035, the one BIND uses). Many servers store zones this way, and it is the format most DNS providers export and import. Being able to read it lets you check a migration, find a lost record and catch mistakes before they take the website or e-mail down. A small zone:$ORIGIN example.com.
$TTL 3600
@ IN SOA ns1.example.net. hostmaster.example.com. (
2026101601 ; serial
3600 ; refresh
1800 ; retry
1209600 ; expire
86400 ) ; minimum
@ IN NS ns1.example.net.
@ IN NS ns2.example.net.
@ IN A 192.0.2.10
@ IN AAAA 2001:db8::10
@ IN MX 10 mail.example.com.
@ IN TXT "v=spf1 a mx -all"
mail IN A 192.0.2.10
www IN CNAME example.com.
_dmarc IN TXT "v=DMARC1; p=none" (example: example.com is a domain reserved for examples, and 192.0.2.10 and 2001:db8::10 are documentation addresses; replace them with yours.)
Each piece of a line
| Piece | What it means |
| $ORIGIN | The domain appended to every name that does not end in a dot. |
| $TTL | The default TTL: it applies to lines that do not carry their own. |
| The name (first column) | @ is the domain itself. www with no dot is www.example.com. A name that ends in a dot is absolute and stays as it is. A blank first column repeats the name from the line above. |
| The TTL (optional number) | How many seconds resolvers may keep the answer. See TTL and caching. |
| IN | The class: Internet. It is on almost every line and you can ignore it. |
| The type | SOA, NS, A, AAAA, CNAME, MX, TXT, SRV, CAA and others. DNS records explained covers what each one does. |
| The data | Whatever the type needs: an IP for A, a priority and a name for MX, quoted text for TXT. |
| ; and ( ) | A semicolon starts a comment. Parentheses let one record span several lines, like the SOA in the example. |
Reading your zone, in this order
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| The dot at the end of a name changes everything. In a zone whose origin is example.com, writing mail.example.com without the dot gives mail.example.com.example.com., a name nobody looks up. Some editors add the dot for you, others do not: always check what was saved. |
| Keep a copy of the zone before you change provider. That file is the record of what the zone held, and it is what you check the new zone against: moving your DNS zone and checking it. |
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Looking at a zone and one line makes no sense? Send us the domain and the line that puzzles you. Open a support ticket |
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