We have seen that Universal Acceptance (UA) for IDNs mean that they can be used anywhere that an ASCII domain name is used.  This is a profound and continuing problem for IDNs.

A study in 2017, carried out by Donuts and ICANN staff, looked at 749 of the Alexa top-1,000 websites and found that only 7% of the sites allowed users to use Internationalised Email Addresses in fields that require an email address to be filled in.

The results of that study support our research team’s previous findings in this area. We have found that many web applications and software tools make assumptions about domain names and email addresses. In previous years we have seen that one of the great challenges facing Universal Acceptance of IDNs is ensuring that the hardcoded assumptions built into applications don’t create barriers to the use of IDNs and EAI addresses. As in previous years, this remains an enormous challenge.

This is an ongoing problem that is not related to particular browsers or infrastructure on the Internet.  Instead, this is a problem for applications that run on the web or in mobile platforms.