On: In search of the perfect URL validation regex

[Buge]

Interestingly it seems http://✪df.ws isn't actually valid, even though it exists. ✪ isn't a letter[1], so it isn't allowed in international domain names. I was looking at the latest RFC from 2010 [2] so maybe it was allowed before that. The owner talks about all the compatibility trouble he had after he registered it [3]. The registrar that he used for it, Dynadot, won't let me register any name with that character, nor will Namecheap.

[1] http://www.fileformat.info/info/unicode/char/272a/index.htm

[2] http://tools.ietf.org/html/rfc5892

[3] http://daringfireball.net/2010/09/starstruck

[X-Istence → Buge]

It's the same way with http://💩.la/ it gets turned into the following using IDNA: xn--ls8h.la.

That is a valid domain name and should be treated as such.

[Buge → X-Istence]

I guess you could argue the definition of "valid". According to the RFC it's

DISALLOWED: Those that should clearly not be included in IDNs. Code points with this property value are not permitted in IDNs.