22

I would like to use a domain name in an example. I know that example.com exists for this purpose, but I would like the domain name not to exist (and not to start existing later). Is there any canonical example of a domain name which is guaranteed not to exist?

a3nm
  • 859
  • 5
  • 11

1 Answers1

36

As per RFC 6761 section 6.4, the domain invalid. and any names falling within .invalid., can be assumed not to exist.

Community
  • 1
a3nm
  • 859
  • 5
  • 11
  • 1
    I wonder what the RFC means by "names falling within .invalid." -- host www.invalid.com has address 173.0.129.46 (so what, exactly is the *legal* hostname that is guaranteed never to resolve? cuz .invalid. is not a legal hostname...) – gigawatt May 11 '17 at 17:34
  • I think this means "hostnames ending with .invalid", I guess the extra dot at the end is just a notation. – a3nm May 11 '17 at 20:53
  • 5
    The `.` at the end refers to the root zone, the one to which all top-level domains belong. It does not mean "substring contained", it means that when normalized to a FQDN ("fully qualified domain name", which implies having the root zone dot at the end), it does not end with `.invalid.` – Jesper Apr 03 '18 at 13:55