[gtld-tech] number of characters in a domain?

Marc Blanchet marc.blanchet at viagenie.ca
Sat Jul 23 13:40:04 UTC 2016

On 23 Jul 2016, at 8:44, Stephane Bortzmeyer wrote:

> On Sat, Jul 23, 2016 at 12:31:15PM +0000,
>  Ryan Finnesey <ryan at finnesey.com> wrote
>  a message of 5 lines which said:
>> I was hoping someone can help me confirm my research.  I am correct
>> that domains are now limited to 67 characters in length including
>> the extension?
> "Extension" is for file names, not for domains.
> Otherwise, easy question, see RFC 1035 :
> 2.3.4. Size limits
> Various objects and parameters in the DNS have size limits.  They are
> listed below.  Some could be easily changed, others are more
> fundamental.
> labels          63 octets or less
> names           255 octets or less

I would like to emphase here that this is the number of octets, not the 
number of characters. For example, if one is using idn, then the idn is 
encoded into punycode and a prefix is added (xn—) therefore costs many 
octets for a single character when encoded.


> Quizz: how many labels does it authorize? :-)

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