[Bug 15254] Don't forbid underscore in host names in URLs

https://www.w3.org/Bugs/Public/show_bug.cgi?id=15254

--- Comment #3 from Brian Campbell <lambda@continuation.org> 2011-12-17 16:14:04 UTC ---
(In reply to comment #1)
> Maybe underscore character should at least be allowed in _sub_domain names
> (foo_bar.example.com) since such subdomains, indeed, do work in real world.
> 
> Domain registrators usually do not allow to use underscore in second-level
> domains (foo_bar.com), but _sub_domains are _not_ subject for this restriction
> since they are created by second-level-domain _owner_ (which includes
> transparent internal redirection by web-server on the fly without even
> assigning DNS-record to each subdomain severally), not registrator at all.

Maybe. If you check the Alexa top million sites CSV, you see several second
level domains with underscores. However, none of them actually resolve, as far
as I can tell, so they are most likely just junk data in Alexa's dataset.
Subdomains do actually work in practice, however. I have yet to see a working
second level domain that includes an underscore.

I am not sure that this restriction should be specified in HTML5, however. If
it's merely a registrar policy, it could change in the future. Also,
distinguishing between registered domains and subdomains is hard, given cases
like .co.uk. I would just as soon leave that part up to the registrars.

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Received on Saturday, 17 December 2011 16:14:09 UTC