When creating URL segments (typically from content name) or simple address, by default, Optimizely only allows characters according to [RFC 1738](🔗), which basically allows ALPHA / DIGIT / '-'/ '\_'/ '~' / '.'/ '$'/.

You can define a custom character set to be used. To do this, update the `UrlSegmentOptions` configuration in the IOC container. When a character set is defined that allows characters outside RFC 1738, the setting `UrlSegementOptions.SupportIriCharacters` should be set to _true_ so that URLs gets properly encoded. Below is an example of a character set that allows unicode characters in the letter category.

`UrlSegmentOptions` also exposes a `CharacterMap` property, where it is possible to define a mapping for unsupported characters, for example 'ö' => 'o'.

## Internationalized Domain Names (IDN)

As explained in [IDN and IRI](🔗), internationalized domain names are registered in punycode format (a way of representing Unicode characters using only ASCII characters).

Internationalized domain names should be registered in their punycode format in the CMS admin view under **Manage Websites**.