Standardizing on IDNA 2003 in the URL Standard

Andrew Sullivan ajs at
Thu Aug 22 18:26:27 CEST 2013

On Thu, Aug 22, 2013 at 04:11:15PM +0100, Anne van Kesteren wrote:
> discussion here which makes matters confusing. What matters is
> IDNA2003 as implemented and deployed throughout the DNS.

Except it's _not_ deployed throughout the DNS.  The ASCII-form is
what's in the DNS.  For the overwhelming majority of cases of valid,
actually deployed IDNA2003 labels that we have ever found, there will
be no change.  And the applications are still doing the work of
translating those labels to Unicode.

IDNA2008 is supposed not only to reduce the number of code points that
are permitted by the protocol.  Among other things, it's also designed
to improve the underlying normalization (NFC, which is better for
these purposes than NFKC according to UTC documents); to permit the
use of certain joiners that our Arabic-script using colleagues insist
are extremely important to them (you should hear the reaction when I
tell Arabic-using people that browsers aren't planning to do IDNA2008
yet); to ensure that every U-label has exactly one A-label and
conversely (which is not true under IDA2003); and still to make
possible the kind of mapping that is required in IDNA2003 while yet
permitting more locale-sensitive treatment in the unusual cases where
that is appropriate.

Given the places the Internet is growing, and if we assume that domain
names will continue to be at all important, the number of IDNs
actually deployed today is a tiny percentage of what it will be in the
near future, especially as more IDN TLDs come online.  We need to fix
the known issues before it really is absolutely too late to do


Andrew Sullivan
ajs at

More information about the Idna-update mailing list