In the Sitefinity Backend go to Administration » Settings » Advanced » System » Site URL Settings » URLRulesClient

The "RegularExpressionFilter" contains all special characters that should be replaced (Ex: Changing the value to "[^\p{L}\-\!\$\(\)\=\@\d_\.]+|\.+$" will not replace single quotes(') ). If the regular expression default value is changed, the setting will show the “Modified” flag as in the image above.

Our recommendation is to change the default regular expression from this:

[^\p{L}\-\!\$\(\)\=\@\d_\'\.]+|\.+$

To this:

[^\p{L}\-\!\(\)\@\d_\']+|\s+$

What is replaced using the suggested regular expression?

The regular expression replaces characters different than:

1. Any character in the ‘Letter’ unicode category
2. Characters - ! ( ) @ ' _
3. Any digit character

For example, these characters will be replaced: "#%&/?¡¨[:;/*+{}[]<>,=.$

Note: We recommend changing the default regular because it was noted that the default regular expression defined in Sitefinity does not replace the = or the $, but these characters are considered invalid in the URLName. The . character is another case that is not always valid.

Examples:

The "Replace with" setting is the character that should replace the special characters.

Apart from that, there are also options to convert the URLs to lower case and to trim it.