Special-use domain name

A special-use domain name is a domain name that is defined and reserved in the hierarchy of the Domain Name System of the Internet for special purposes. The designation of a reserved special-use domain is authorized by the Internet Engineering Task Force (IETF) and executed, maintained, and published by the Internet Assigned Numbers Authority (IANA).

Reserved domain names

The following list comprises the domain names list by IANA in the category of special-use domain names.

Domain	Purpose	Authority document
alt.	preventing name collisions with DNS	RFC 9476
6tisch.arpa.	IETF 6TiSH working group	RFC 9031
10.in-addr.arpa.	private network reverse mapping	RFC 6761
16.172.in-addr.arpa.
17.172.in-addr.arpa.
18.172.in-addr.arpa.
19.172.in-addr.arpa.
20.172.in-addr.arpa.
21.172.in-addr.arpa.
22.172.in-addr.arpa.
23.172.in-addr.arpa.
24.172.in-addr.arpa.
25.172.in-addr.arpa.
26.172.in-addr.arpa.
27.172.in-addr.arpa.
28.172.in-addr.arpa.
29.172.in-addr.arpa.
30.172.in-addr.arpa.
31.172.in-addr.arpa.
168.192.in-addr.arpa.
170.0.0.192.in-addr.arpa.	NAT64 prefix discovery (RFC 7050)	RFC 8880
171.0.0.192.in-addr.arpa.
ipv4only.arpa.
254.169.in-addr.arpa.	Use in multicast DNS (mDNS)	RFC 6762
8.e.f.ip6.arpa.
9.e.f.ip6.arpa.
a.e.f.ip6.arpa.
b.e.f.ip6.arpa.
home.arpa.	Non-unique use on residential networks	RFC 8375
example.	documentation, tutorials, etc.	RFC 6761
example.com.	use in documentation, tutorials, testing	RFC 6761
example.net.
example.org.
invalid.	Avoidance of confusion and errors per RFC 2606	RFC 6761
local.	Used for Multicast DNS	RFC 6762 (Section 3)
localhost.	Reserved to avoidance of confusion and errors	RFC 6761
onion.	Anonymous onion service	RFC 7686
test.	Avoidance of confusion, allowing use for documentation and network testing	RFC 6761

See also

• Reserved top-level domains