Cleaning Up WordPress’ Default Front-End Boilerplate Code

/**
 * Remove unnecessary wp_head actions and output
 */
remove_action ( 'wp_head', 'rsd_link' ); // remove xml rpc
remove_action(  'wp_head', 'wlwmanifest_link' ); // remove manifest
remove_action(  'wp_head', 'wp_shortlink_wp_head' ); // remove shortlink
remove_action( 'wp_head', 'rest_output_link_wp_head', 10 );
remove_action( 'wp_head', 'wp_oembed_add_discovery_links', 10 );
remove_action( 'template_redirect', 'rest_output_link_header', 11, 0 );

/**
* Remove the output of WP version
*/
function remove_wp_version() {
  return '';
}

add_filter( 'the_generator', 'remove_wp_version' ) ;

/**
 * Disable emojis
 */
function disable_emojis() {
  remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
  remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
  remove_action( 'wp_print_styles', 'print_emoji_styles' );
  remove_action( 'admin_print_styles', 'print_emoji_styles' );
  remove_filter( 'the_content_feed', 'wp_staticize_emoji' );
  remove_filter( 'comment_text_rss', 'wp_staticize_emoji' );
  remove_filter( 'wp_mail', 'wp_staticize_emoji_for_email' );
  add_filter( 'tiny_mce_plugins', 'disable_emojis_tinymce' );
  add_filter( 'wp_resource_hints', 'disable_emojis_remove_dns_prefetch', 10, 2 );
  add_filter( 'emoji_svg_url', '__return_false' ); // remove dns prefetch for emoji
}

add_action( 'init', 'disable_emojis' );

/**
 * Filter function used to remove the tinymce emoji plugin.
 *
 * @param array $plugins
 * @return array Difference betwen the two arrays
 */
function disable_emojis_tinymce( $plugins ) {
  if ( is_array( $plugins ) ) {
    return array_diff( $plugins, array( 'wpemoji' ) );
  } else {
    return array();
  }
}

/**
 * Remove emoji CDN hostname from DNS prefetching hints.
 *
 * @param array $urls URLs to print for resource hints.
 * @param string $relation_type The relation type the URLs are printed for.
 * @return array Difference betwen the two arrays.
 */
function disable_emojis_remove_dns_prefetch( $urls, $relation_type ) {
  if ( 'dns-prefetch' == $relation_type ) {
    /** This filter is documented in wp-includes/formatting.php */
    $emoji_svg_url = apply_filters( 'emoji_svg_url', 'https://s.w.org/images/core/emoji/2/svg/' );

    $urls = array_diff( $urls, array( $emoji_svg_url ) );
  }

  return $urls;
}

/**
 * Disable unauthenticated REST API requests
 */
function disable_unauthenticated_rest( $result ) {

  // If a previous authentication check was applied, pass that result along without modification.
  if ( true === $result || is_wp_error( $result ) ) {
    return $result;
  }

  // disable response if not logged in
  if ( ! is_user_logged_in() ) {
    return new \WP_Error(
        'access_denied',
        __( 'Access denied' ),
        array( 'status' => 401 )
    );
  }

  return $result;
}

add_filter( 'rest_authentication_errors', 'disable_unauthenticated_rest' );

/**
 * Remove oembed script
 */
function remove_oembed_script(){
  wp_deregister_script( 'wp-embed' );
}

add_action( 'wp_footer', 'remove_oembed_script' );

/**
 * Remove Gutenberg CSS
 * Obviously you should not add this if you are using Gutenberg blocks
 */
function remove_block_css() {
  wp_dequeue_style( 'wp-block-library' );
}

add_action( 'wp_print_styles', 'remove_block_css', 100 );

/** 
 * Remove jQuery Migrate
*/
function remove_jquery_migrate( $scripts ) {
  if ( ! is_admin() && isset( $scripts->registered['jquery'] ) ) {
    $script = $scripts->registered['jquery'];
    if ( $script->deps ) {
      $script->deps = array_diff( $script->deps, array( 'jquery-migrate' ) );
    }
  }
}

add_action( 'wp_default_scripts', 'remove_jquery_migrate' );