IDN – Internationalised Domain Names

IDN stands for "Internationalised Domain Name" — domain names that contain characters beyond the standard a-z, 0-9, or hyphens.

Below are some examples of top-level domains and the characters they support:

.SE
Allowed characters: a-z, å, ä, ö, æ, ø, 0-9, "-"

.EU
Allowed characters: a-z, å, ä, ö, ü, é, 0-9, "-"

.NU
Allowed characters: a-z, å, ä, ö, ü, é, 0-9, "-"

.COM .NET .ORG .BIZ .INFO
Allowed characters: a-z, å, ä, ö, ü, é, 0-9, "-"

.DK
Allowed characters: a-z, å, ä, ö, ü, é, æ, ø, 0-9, "-"

.PL
Allowed characters: a-z, å, ä, ö, ü, é, 0-9, "-"

.ES
Does not support å, ä, or ö.