Validation code for IDN (Domain) with regex (regular expression)

Question

I want to check domains with regex. My old code was:

/^([a-z0-9]+([-a-z0-9]*[a-z0-9]+)?.){0,}([a-z0-9]+([-a-z0-9]*[a-z0-9]+)?){1,63}(.[a-z0-9]{2,7})+$/i

It is okey but this code doesn't validate IDNs (internationalized domain names) such as öü.com or öü.öü

My domain format is:

• example.com

Besides, I don't want:

• www.example.com
• http://example.com
• http://www.example.com

Important note: user can add the domains;

• with 2 extension like example.co.uk

Answer 1

Idn's such as भारत.icom.museum use Punycode encoding, as defined in RFC 3492, before submission for DNS resolution.

It seems that you're using php, based on that, you should use the idn_to_ascii() function to convert the idn's, ex:

echo idn_to_ascii("भारत.icom.museum");
//xn--h2brj9c.icom.museum

Answer 2

You can add support for IDNs by replacing a-z by \pL