https://wpvkp.com/enable-dns-prefetch-wordpress-instant-articles-plugin -- This code will help you to enable dns prefetch in wordpress.

functions.php

<?php // ************* DON'T COPY ME ***************

/* This is for next and previous post */
function wpvkp_dnsprefetch_next_previous() {
 
  $nxt = get_next_post();
  $prv = get_previous_post();

  if ( !empty( $nxt ) ) {
    echo '<link rel="prefetch" href="'.get_permalink( $nxt-&gt;ID ).'" />
      <link rel="prerender" href="'.get_permalink( $nxt-&gt;ID ).'" />';
  }

  if ( !empty( $prv ) ) {
    echo '<link rel="prefetch" href="'.get_permalink( $prv-&gt;ID ).'" />
      <link rel="prerender" href="'.get_permalink( $prv-&gt;ID ).'" />';
  }
}
add_action( 'wp_head', 'wpvkp_dnsprefetch_next_previous', 10 );