Meaw.fi

Rewrites a zone master file into a readable, canonical form: one $TTL and one $ORIGIN at the top, every owner name written out in full, and aligned columns.

Zone files have a lot of syntax that is valid but hard to read. An indented line silently inherits the previous record's owner name; $ORIGIN and $TTL can each change part-way through, so the same label or the same bare record means different things in different places; TTL and class can be left out entirely. This resolves all of that, then checks the result for the usual problems — a missing or duplicated SOA, no NS at the apex, a CNAME sharing a name with other records, unbalanced parentheses, and domain names that lost their trailing dot and quietly expanded into nonsense.

One $ORIGIN

Every name is resolved against whichever $ORIGIN was in effect where it was written, then re-expressed relative to the first $ORIGIN in the file. Later $ORIGIN lines are dropped. Names in RDATA are rewritten too — the target of a CNAME, an MX exchange, an SRV target — not just owner names, since those would otherwise change meaning once the directive they were written under disappears.

A later $ORIGIN outside the first one's tree cannot be expressed relative to it. Those records are written out fully qualified instead, and a warning says so.

One $TTL

Every record is given the TTL that was in effect where it was written — its own, or the $TTL above it. The one covering the most records becomes the single $TTL at the top of the file (ties go to whichever came first), and the rest of the $TTL lines are dropped. A record matching that default is left bare; one that differs gets its TTL written in, so no record's TTL depends on how far up the file you look. Values are compared as durations, so 1h and 3600 count as the same TTL.

A file with no $TTL at all is left alone — every TTL stays exactly as written, since hoisting one in would change what the bare records mean. Records above the first $TTL are the one case where this does change the zone: they used to fall back to the SOA minimum, and a warning names them.

Explicit owner names

An indented record inherits the owner name of the record above it. Every output line repeats the owner explicitly, so no line depends on the one before it any more.

Explicit class

A record with no class gets one written in — inherited from the last record that stated one, or IN if none did, which is what BIND itself would use.

Left alone on purpose

$INCLUDE and $GENERATE are passed through byte-for-byte: the first cannot be read (nothing is ever fetched) and the second is not expanded, so neither is reformatted or checked. Any record with a type this tool does not recognise is also passed through unchanged rather than reformatted into something possibly wrong.