Markus Scherer at
Wed Aug 13 21:00:54 CEST 2014

On Wed, Aug 13, 2014 at 11:54 AM, Andrew Sullivan <ajs at>

> On Wed, Aug 13, 2014 at 11:41:29AM -0700, Markus Scherer wrote:
> > One big reason why sharp s and sigma are problematic in IDNA2008 is that
> > users have gotten used to domain names being case-insensitive
> Sort of, and those are certainly not the only cases.  For instance,
> ECOLE.CA and will match, but é <>
> does not match ECOLE.CA
> (which is unexpected for French-from-France readers) and ÉCOLE.CA
> <http://xn--cole-9oa.CA>
> doesn't work at all.

It does with UTS #46.

There's no getting around this, however, because the case-folding
> rules outside the ASCII range are far more complicated than "add
> 0x20", and therefore simple case folding doesn't help.

So what? Case folding is well-defined by Unicode and implementations are
easily available. It's also built into the UTS #46 mapping.

Worse, domain names are not case-insensitive, but case-insensitive
> _for matching_.  DNS is still case-preserving.

>From the user's perspective, and from how browsers behave, there is no

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