Allow WordPress REST API Requests While Restricted Site Access is Active

unrestrict-rest-api.php

<?php
/**
 * Plugin Name: Unrestrict REST API
 * Plugin URI: https://philipnewcomer.net/2016/05/allow-rest-api-restricted-site-access/
 * Description: Allows REST API requests while Restricted Site Access is enabled.
 * Version: 0.1.0
 * Author: Philip Newcomer
 * Author URI: https://philipnewcomer.net
 */

/**
 * Filter Restricted Site Access to allow REST API requests.
 *
 * @param bool   $is_restricted Whether access is restricted.
 * @param object $wp            The WordPress object.
 *
 * @return bool Whether access should be restricted.
 */
function pn_unrestrict_rest_api( $is_restricted, $wp ) {

	if ( ! empty( $wp->query_vars['rest_route'] ) ) {
		return false;
	}

	return $is_restricted;
}
add_filter( 'restricted_site_access_is_restricted', 'pn_unrestrict_rest_api', 10, 2 );