XF 1.1 How to only allow certain characters for usernames.

[ix2013]

How can I only allow a-z A-Z, numbers and _ in usernames on registration?

 

[Paul B]

http://xenforo.com/community/threads/a-new-editor-and-much-much-more.50519/page-26#post-552394

For your specific requirements: ^[a-zA-Z0-9_]+$