Meaw.fi

Each line is searched for one IPv4 or IPv6 address and one hostname, in either order — 192.0.2.10 host.example.com, host.example.com,192.0.2.10, an /etc/hosts line, whatever. Comments after ; or # are ignored.

Zone files work too. Lines with an A or AAAA record use their owner name (an indented line inherits the one above, @ means the origin), and relative names are completed from the $ORIGIN lines in the pasted text. PTR records are read the other way round — the owner is the address — so a reverse zone can be turned back into A records, or re-sorted into other reverse zones. Every other record type is skipped.

Forward writes an A or AAAA record per name and address, sorted by name, each in the most specific forward zone it falls in. Several addresses for one name are all kept. A short name with no domain (web1) and no $ORIGIN above it is not guessed at — it goes in a separate “no domain” block, as written.

Reverse puts each record in the most specific reverse zone it falls in, and each zone gets its own block with a $ORIGIN header and owner names relative to it. A prefix that is not on a zone boundary is split into the zones it covers — /22 becomes four /24 zones, 2001:db8::/30 four /32s. Anything longer than /24 uses its enclosing /24, since classless delegation is not handled.

Records outside every zone are collected in a last block, written fully qualified. Leave the zones empty to get everything that way.