Username Character Restriction in User Registration Integration

Hi,
I'm using the option "User Registration Integration" so if someone registers for an event they can choose a username and password but I need to restrict the character that the user can type in the username, especially blank space.
How can achieve this?

Thanks
Nancy

Hi Nancy

Joomla does not have any special requirement for username, so we do not have that restriction, too. Space character is accepted in Joomla for username, so we do not have that restriction

Tuan