How to do extra username validation on new user registraiton

Hi,
You can use the ‘wppb_check_form_field_default-username’ filter to achieve that.

Here’s a code sample to add some extra validation to the username field:

//Extra validation for username field
function wppb_extra_username_validation( $message, $field, $request_data, $form_location){
    if ('add your extra validation here'){
            return __( 'Add your error message here.', 'profilebuilder' );
        }
    return $message;
}
add_filter('wppb_check_form_field_default-username','wppb_extra_username_validation', 10, 4);

Make sure to add your own validation conditions and desired error message.

No worries, glad it works! If you find Profile Builder useful, please consider leaving a review.