Browser IDN display policy: opinions sought

Andrew Sullivan ajs at
Fri Dec 9 18:49:23 CET 2011

On Fri, Dec 09, 2011 at 11:12:29AM +0000, Gervase Markham wrote:
> A (IE, Chrome): Unicode if the (single) 'language' of the string is
> configured in the options, Punycode otherwise.

The problem with this, of course, is that in many cases there's no way
to tell what language a string is in.  If you get things all in the
Arabic Script, for instance, what language are you in?  And Latin is a
disaster for this.  

It would be quite another matter if there were a way for a zone
operator to publish somehow what languages (or maybe scripts?) they
support.  In that case, you could look it up and know what to do (you
might not even have to do this quickly).

> B (Firefox, Opera): Unicode if the TLD is in a whitelist, Punycode
> otherwise. Arbitrary script mixing permitted (registry policy used to
> prevent abuse).

The problem here has always been both the notion of TLD and the
whitelist maintenance.  The list is, in effect, a
lookaside root list, and it makes me extremely uncomfortable.
Moreover, what do you do about things lower in the tree?
> C (Safari): Unicode if the script is in a whitelist (which by default
> does not include Cyrillic or Greek), Punycode otherwise. Not sure about
> script mixing.

This approach sucks in all the ways you say.  I think it is the worst

I think that the right approach would be A _if_ you could get the
advantages of B automatically somehow.  At the moment, however, I
think all the answers are bad ones.

> It has been suggested that Firefox switch to a Type A policy. As it is,
> the mix of policies means that the goal of universal acceptability is
> not being met anyway. Firefox switching to Type A would also not meet
> that goal by itself, but one could argue that there's a bit more
> consistency to browser behaviour.

But it's consistency that requires users to have some theory about
domain name registration, I think, and also to "know the language"
they're going to see.  

Note, too, that if the root zone expands the way it sometimes
threatens to, the whitelist approach will become impractical without
an awful lot of failures.


Andrew Sullivan
ajs at

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