Out of curiosity, does anyone know what's the maximum length (in characters) for a domain name?

Let's exclude the http://www.

I know the maximum length of an url is about 2000 chars. But here I'm more ineterested in just the domain part or the url.

On Wikipedia they say: "The full domain name may not exceed a total length of 253 characters in its external dotted-label specification." But what does that mean?

  1. 253 characters is the maximum length of full domain name, including dots: e.g. www.example.com = 15 characters.

  2. 63 characters in the maximum length of a "label" (part of domain name separated by dot). Labels for www.example.com are com, example and www.

This is an example of the domain with longest possible label (a fully working website BTW): http://www.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk.com/. The domain name length = 71 characters.

This will be an example of longest domain name: abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcde.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk.com

  • 1
    +1. It is also explained here: en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names – Ritesh Jul 17 '11 at 13:04
  • If you want an easy way to break many online systems out there, try signing up or using one of these with an email address @ one of the domains above. – Tim Fountain Jul 18 '11 at 17:56
  • 3
    Maybe you want to add a normative reference: RFC 1123, chapter 2.1 defines the 63 character limit. But where is the 253 limit defined? – Thomas Weller Apr 22 '16 at 6:54

Not the answer you're looking for? Browse other questions tagged or ask your own question.