.localhost
Introduced	1999
TLD type	Reserved top-level domain
Status	Reserved to prevent actual use
Registry	IANA
Sponsor	None
Intended use	Identifies the current local computer; reserved at the top level of the DNS to prevent remote addresses that conflict with this
Actual use	Much software, including Web browsers, lets you access local host this way
Registration restrictions	No registrations are possible, as this domain is not in the root
Structure	Has no structure; it's used directly as a hostname
Documents	RFC 2606
Dispute policies	None
Website	None

.localhost is a reserved top-level domain not intended for practical use in the global Domain Name System (DNS). It was defined in June 1999 by RFC 2606, along with .example, .invalid, and .test.

Its explicit reservation is intended to avoid confusion with the common hostname, localhost, which is the name of the loopback interface in most TCP/IP systems. The ".localhost" TLD has traditionally been statically defined in host DNS implementations as having an A or AAAA (address) records pointing to the loopback IP addresses 127.0.0.1 (IPv4) and ::1 (IPv6) and is therefore reserved for such use. Any other use would conflict with widely deployed algorithms relying on this use.