| Introduced | 1999 |
|---|---|
| TLD type | Reserved top-level domain |
| Status | Reserved to prevent conflict and confusion |
| Intended use | When necessary to show an address guaranteed to be invalid |
| Actual use | Session Initiation Protocol, for identity protection; address munging e.g. on Usenet |
| Documents | RFC 2606, 3325 |
The name invalid is reserved by the Internet Engineering Task Force (IETF) as a domain name that may not be installed as a top-level domain in the Domain Name System (DNS) of the Internet. [1]
In 1999, the Internet Engineering Task Force reserved the DNS labels example , invalid, localhost , and test so that they may not be installed into the root zone of the Domain Name System.
The reasons for reservation of these top-level domain names is to reduce the likelihood of conflict and confusion. [1] This allows the use of these names for either documentation purposes or in local testing scenarios.
This top-level domain is sometimes used as a pseudo domain name in Uniform Resource Identifiers (URIs) to convey either an error condition or in use of privacy protection. A notable instance of this usage is in the Session Initiation Protocol (SIP) where the domain name anonymous.invalid in a SIP URI indicates hiding of a caller's identity. [2]