Username as Digits only

Hi @illuder,

To set username as a digit only, you will need to paste the following code in your active theme’s functions.php file.

Here is the code:

add_action( 'user_registration_validate_user_login','ur_validate_username_field',10,4);
function ur_validate_username_field($single_form_field, $data, $filter_hook, $form_id) {	
	$field_label = isset( $data->label ) ? $data->label : '';
	$value = isset( $data->value ) ? $data->value : '';
	if( 1 !== preg_match('~[0-9]~', $value ) ) {
	    add_filter( $filter_hook, function ( $msg ) use ( $field_label ) {
	        return __( $field_label . 'should contain a  number.', 'user-registration' );
	   });
	}
} 

Do let me know whether it helps or not and I will get back to you.

Thanks and Regards!