Standardizing on IDNA 2003 in the URL Standard

Patrik Fältström paf at
Wed Aug 21 20:21:44 CEST 2013

On 21 aug 2013, at 11:07, Gervase Markham <gerv at> wrote:

> With regard to any incompatibilities, particularly around sharp-S and
> final sigma, my understanding and expectation is that the registries
> most concerned with those characters (e.g. the Greek registry for final
> sigma) were in agreement that IDNA2008 was the correct way forward, and
> that any breakage caused by the switch was better than the breakage
> caused by not moving.

Correct. The incompatibility is that sharp-S and final sigma in IDNA2008 is not mapped to other characters. This implies that those characters finally can be used in for example domain names.

When communicating with specifically people registering domain names in German they did acknowledge that as domain names that sort of uses sharp-S has been registered with double-S instead, but now they have to introduce the sharp-S as well. This either the registrant can do themselves before someone is grabbing the domain at sunrise or similar.

But, the problem is more or less the same as what happened when introducing IDN in Sweden, Germany and other countries where earlier for example ä has been mapped to a or ae depending on what the registrant want. We will always get those problems when new characters are introduced in DNS. We have done it before, and we will do it again.

I.e. the message was clear that these kind of mapping errors creates problems that are compensated multiple times over and over again by a) getting a 1:1 mapping between A-Label and U-label, b) getting a unicode-version-independent standard and c) having the ability to use sharp-S in domain names and not only double-S.


More information about the Idna-update mailing list