May 28, 2017 - Servants of Grace

add_action( 'wp_head', function() { if ( is_singular() ) { // Get the full-size featured image URL $img = get_the_post_thumbnail_url( get_the_ID(), 'full' ); if ( $img ) { // Output preload tag with imagesrcset & imagesizes attributes for responsiveness printf( '' . "\n", esc_url( $img ), pathinfo( $img, PATHINFO_EXTENSION ) ); } } } );