REST API – provides an interface for interacting with your site running on the WordPress CMS using json requests.
In recent versions of the engine, the REST API has been included in the core. This means that it starts working automatically after installing a fresh copy of WordPress, adding a line on each page of the site: . If you create content only in the admin panel of your site, then this functionality is not needed.
For complete shutdown REST API in yours WordPress site add code below in yours theme function.php file:
add_filter('rest_enabled', '__return_false');
remove_action( 'xmlrpc_rsd_apis', 'rest_output_rsd' );
remove_action( 'wp_head', 'rest_output_link_wp_head', 10, 0 );
remove_action( 'template_redirect', 'rest_output_link_header', 11, 0 );
remove_action( 'auth_cookie_malformed', 'rest_cookie_collect_status' );
remove_action( 'auth_cookie_expired', 'rest_cookie_collect_status' );
remove_action( 'auth_cookie_bad_username', 'rest_cookie_collect_status' );
remove_action( 'auth_cookie_bad_hash', 'rest_cookie_collect_status' );
remove_action( 'auth_cookie_valid', 'rest_cookie_collect_status' );
remove_filter( 'rest_authentication_errors', 'rest_cookie_check_errors', 100 );
remove_action( 'init', 'rest_api_init' );
remove_action( 'rest_api_init', 'rest_api_default_filters', 10, 1 );
remove_action( 'parse_request', 'rest_api_loaded' );
remove_action( 'rest_api_init', 'wp_oembed_register_route' );
remove_filter( 'rest_pre_serve_request', '_oembed_rest_pre_serve_request', 10, 4 );
remove_action( 'wp_head', 'wp_oembed_add_discovery_links' );
remove_action( 'wp_head', 'wp_oembed_add_host_js' );