How to hook into user registration process Before user registers
You need to create your own hook for registration_errors filter: add_filter( ‘registration_errors’, ‘wpse8170_registration_errors’, 10, 3 ); function wpse8170_registration_errors( $errors, $sanitized_user_login, $user_email ) { if ( /* something happens */ ) { $errors->add( ‘myexception_code’, ‘This is my message’ ); } return $errors; }